Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12−xTixO19

Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12−xTixO19

Journal Pre-proofs Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12-xTixO19 D.A. Vinnik...

1MB Sizes 1 Downloads 84 Views

Journal Pre-proofs Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12-xTixO19 D.A. Vinnik, V.E. Zhivulin, A.Yu. Starikov, S.A. Gudkova, E.A. Trofimov, A.V. Trukhanov, S.V. Trukhanov, V.A. Turchenko, V.V. Matveev, E. Lahderanta, E. Fadeev, T.I. Zubar, M.V. Zdorovets, A.L. Kozlovsky PII: DOI: Reference:

S0304-8853(19)33458-4 https://doi.org/10.1016/j.jmmm.2019.166117 MAGMA 166117

To appear in:

Journal of Magnetism and Magnetic Materials

Received Date: Revised Date: Accepted Date:

3 October 2019 21 October 2019 5 November 2019

Please cite this article as: D.A. Vinnik, V.E. Zhivulin, A.Yu. Starikov, S.A. Gudkova, E.A. Trofimov, A.V. Trukhanov, S.V. Trukhanov, V.A. Turchenko, V.V. Matveev, E. Lahderanta, E. Fadeev, T.I. Zubar, M.V. Zdorovets, A.L. Kozlovsky, Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12-xTixO19, Journal of Magnetism and Magnetic Materials (2019), doi: https://doi.org/10.1016/ j.jmmm.2019.166117

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2019 Published by Elsevier B.V.

Influence of titanium substitution on structure, magnetic and electric properties of barium hexaferrites BaFe12-xTixO19 D.A. Vinnik1, V.E. Zhivulin1, A.Yu. Starikov1, S.A. Gudkova1, 2, E.A. Trofimov1, A.V. Trukhanov1, 3, 4, S.V. Trukhanov1, 3, 4, V.A. Turchenko5, 6, V.V. Matveev7, E. Lahderanta8, E. Fadeev8, T.I. Zubar1, 4, M.V. Zdorovets9, A.L. Kozlovsky9 1Laboratory

of single crystal growth, South Ural State University, 454080, Chelyabinsk, Lenin Prospect, 76, Russia 2Moscow Institute of Physics and Technology (State University), 141700, Dolgoprudny, Institutskiy per. 9, Russia 3National University of Science and Technology MISiS, 119049, Moscow, Leninsky Prospekt, 4, Russia 4Scientific Practical Materials Research Centre of NAS of Belarus, 220072, Minsk, P. Brovki str., 19, Belorussia 5Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980, Dubna, 6 Joliot-Curie Str., Russia 6Donetsk Institute of Physics and Technology named after O.O. Galkin of the NASU, 03680 Kiev, 46 Nauki Ave, Ukraine 7Saint Petersburg State University, 199034, Saint Petersburg, 7/9 Universitetskaya nab., Russia 8Lappeenranta University of Technology, 53850, Lappeenranta, Finland 9Institute of Nuclear Physics, 050032, Ibragimova str.1, Nur-Sultan, Kazakhstan Corresponding author: D.A. Vinnik: [email protected], +7-951-457-22-86 D.A. Vinnik [email protected] V.E. Zhivulin [email protected] A.Yu. Starikov [email protected] S.A. Gudkova [email protected] E.A. Trofimov [email protected] A.V. Trukhanov [email protected] S.V. Trukhanov [email protected] V.A. Turchenko [email protected] V.V. Matveev [email protected] E. Lahderanta [email protected] E. Fadeev [email protected] T.I. Zubar [email protected] M.V. Zdorovets [email protected] A.L. Kozlovsky [email protected]

ABSTRACT— Titanium substituted BaFe12-xTixO19 (x ≤ 1) barium hexaferrites have been synthesized using the solid phase method. The phase purity and the crystal structure of the obtained solid solutions have been studied by X-ray diffraction. It was found that the unit cell parameters change a non-monotonically. The a parameter has a maximum of 5.896 Å at x = 0.25 and then it decreases almost linearly down to 5.886 Å at x = 1. The c parameter almost linearly increases from 23.216 Å up to 23.282 Å with x increasing. It has been discovered that titanium cations are located in the following positions: 4fIV tetrahedral and octahedral 4fVI and 12k ones. Results of the Mossbauer and Raman spectrometry confirm the established substitution mechanism. The homogeneous ferrimagnetic ordering is detected by magnetic measurements down to ~ 35 K. Below this temperature the noncollinear magnetic structure is formed as a result of Fe2+ cations change in the spin state from high to low configuration. Magnetization for all the samples is saturated at room temperature in fields of ~ 1 T. The saturation magnetization decreases from ~ 70.6 emu/g for x = 0.25 to ~ 56.7 emu/g for x = 1. The real part of the dielectric constant has value of ~ 0.2 for all the samples and gradually decreases at heating from room temperature up to ~ 500 K, after which it begins to increase sharply. The dielectric loss tangent has a maximum in the region of ~ 500 K and reaches a value of ~ 0.25 at a frequency of 104 Hz. With increasing the substitution level, the dielectric constant and the dielectric loss of all the samples increase. Keywords: M-type barium hexaferrites; titanium substitution; crystal structure; magnetization; Mössbauer and Raman spectra; indirect exchange interactions.

I. INTRODUCTION Complex iron oxides have a great scientific and practical significance [1-4]. These compounds have mainly three crystal structure types such as a perovskite [5], spinel [6] and magnetoplumbite [7]. All complex iron oxides have a Curie point above room temperature [8]. This advantage makes this class of compounds promising for practical use as a magnetic material [9]. However, a spontaneous magnetic moment is also important parameter in order to a compound may be used in practice. Therefore, the M-type AFe12O19 (A = Sr, Ba) hexaferrites with a magnetoplumbite structure are excellent candidates for such magnetic materials. This is the simplest class of all ferrites with a hexagonal structure. More than 90% of permanent magnets are produced all over the world based on these compounds. They are a semiconductors with high value of bandgap with resistivity of ~ 109 Ohm*cm order at room temperature. They have ferrimagnetic structure and total magnetic moment of 20 μB in the ground state [10]. Besides a high Curie point, high spontaneous magnetic moment and high room temperature resistivity M-type hexaferrites have also high values of permittivity and permeability [11-13]. They are also chemically stable in a wide temperature range in air. Such properties make also the M-type hexaferrites promising for practical use as a microwave absorption material [14]. Reflection loss of these compounds is determined by natural ferromagnetic resonance and resonances of domain boundaries [15] and may be tuned by chemical substitution. For BaFe12xGaxO19 (x ≤ 1.2) hexaferrites the resonance frequency changes from 49.6 GHz up to 50.5 GHz with minimum of 49.1 GHz at x = 0.6. The bandwidth increases from 3.5 to ~ 5 GHz. The reflection loss changes slightly around ~ -18 dB with the exception for the x = 0.9 when it reaches -16 dB [16]. From scientific point of view it is very necessary to understand the reason of a large spontaneous polarization at room temperature recently discovered in the M-type hexaferrites with substitution of the iron by diamagnetic ions [17-21]. It should be noted that the magnetoelectric coefficient and magnetocapacitance of the substituted M-type hexaferrites can be obtained larger than for the well-known BiFeO3 orthoferrite applying a modified ceramic technique. The residual polarization was also observed in case of Al3+ and In3+ substitutions at room temperature [22-23]. To understand such ferroelectric behavior the refinement of crystal structure of the barium hexaferrites with isovalent substitution has been carried out in frameworks of two possible space groups. The centrosymmetric P63/mmc (No. 194) and noncentrosymmetric P63mc (No. 186) space groups have been used that allowed to reveal reasons of appearance of nonzero dipole electric moment. The distortion of neighboring FeO6 oxygen octahedrons around the 6c crystallographic positions is a reason of appearance of local nonzero electric dipoles [23]. Such description of the crystal structure and appearance of spontaneous polarization for M-type hexaferrites is true in case of isovalent substitution when the charge state of Fe3+ cations remains the same. At heterovalent substitution the Fe2+ and Fe4+ cations may appear [24-31]. Fe4+ cation is unstable in octahedral oxygen coordination and the phenomenon of so called charge disproportionation Fe4+ → Fe3+ + Fe5+ can be observed [31]. Therefore, in case of substitution by such cations as Mg2+, Zn2+, Cu2+, Ni2+ etc., the Fe3+ and Fe5+ cations appears. This is also interesting case. In present paper it is reported the effect of diamagnetic heterovalent substitution by Ti4+ cations on the structure and magnetodielectric properties of barium hexaferrite. Some information has already been given in the literature on this kind of substitution [32-40]. In such case the Fe2+ cations are present. Fe2+cation in octahedral oxygen coordination may undergo a spin crossover phenomenon from high-spin (HS) state with total spin of S = 2 to low-spin (LS)

state with S = 0 according to crystal field energy [41]. It is interesting to note that magnetoelectric properties of diamagnetically substituted hexaferrites determined by aligned local Fe3+ - Fe3+(D3+) dipoles may be also improved by the appearance and arrangement of local Fe3+ - Fe2+(D4+) dipoles. II. EXPERIMENTAL For preparation of the substituted BaFe12-xTixO19 with x ≤ 1 polycrystalline samples the high purity Fe2O3, TiO2 and BaCO3 have been used in ‘two-steps’ conventional solid state sintering method. Firstly, the oxides and carbonate have been mixed with design ratio. Then the precalcination has been performed at 1200oC in air during 6 h. Final synthesis was carried out at 1300oC in air during 6 h. After synthesis the sample has been slowly cooled (100oC*h-1) [42]. The formation of BaFe12-xTixO19 powders can be represented as follows:

1  12  x  BaCO3    Fe2O3   x TiO2  BaFe12 xTixO19  CO2   xO2  4  2 

(1)

The phase composition as well as crystal parameters of hexaferrites have been analyzed by Malvern Panalytical Empyrean X-ray diffractometer in Cu-Kα radiation λ = 1.541874 Å [43]. The powder diffraction software package HighScore Plus [44] which includes the standards of the ICDD [45] has been used to determine the quantitative phase analysis. The Rietveld analysis [46] realized within the FullProf software [47] has been also used. 57Fe Mössbauer spectra of the powdered sample were collected at room temperature in transmission geometry using a constant-acceleration spectrometer equipped with a 57Co/Rh source [48]. Raman scattering spectra were measured in back-scattering geometry at room temperature through a 50× microscope objective using a Renishaw inVia micro-Raman spectrometer equipped with an argon laser (514.5 nm, max cw power Pex = 10 mW) [49]. Temperature dependence of specific magnetization in zero field cooled (ZFC) and field cooled (FC) regimes was measured in 4-370 K interval in field of 1 T by Liquid Helium Free High Field Measurement System (VSM) [50]. Field dependence of specific magnetization was measured at 300 K [51]. The electrical properties were characterized by the resistivity and real part of permittivity 𝜀′ which was measured using LRC-meter up to 100 kHz in the wide temperature range (300-800 K) [52]. III. RESULTS AND DISCUSSION Fig. 1 presents X-ray phase analysis of substituted BaFe12-xTixO19 hexaferrites. The P63/mmc (No. 194) space group has been used for analysis of XRD patterns. As can be seen from the figure, the results of XRD analysis confirm the preparation of solid solutions of barium hexaferrite substituted by titanium cations with an upper solubility limit of 1. During the Rietveld analysis of the transition metal sites occupancy the certain structural model was considered. It was assumed that titanium cations are located in the following positions : 4fIV tetrahedral and octahedral 4fVI and 12k ones. The results of the crystal structure refinement performed in such model, firstly, are optimal and, secondly, are consistent with the results of magnetic measurements. This is clearly seen from Table 1. χ2 varies in range of 1.82 2.14. This is a satisfactory result. With titanium cations content increasing a non-monotonic change in the parameters of the unit cell is observed (Fig. 2). The a parameter has a maximum of 5.896 Å at x = 0.25. Then it

decreases almost linearly down to 5.886 Å at x = 1. The c parameter almost linearly increases from 23.216 Å up to 23.282 Å with x increasing. The V volume of the unit cell behaves according to the parameters. It has a maximum at x = 0.25 and an inflection point at x = 0.75. This non-monotonic behavior of the unit cell parameters can be explained by the change in the radii of iron cations during heterovalent substitution by titanium cations and the distribution of substitutional cations in crystallographic positions. So, the Fe3+ cation in the oxygen octahedral coordination in the HS state has an ionic raidius of 0.785 Å, and in the LS state its ionic raidius is 0.690 Å [53]. At the same time, the Ti4+ cation in octahedral coordination has an ionic radius of 0.745 Å. It should be especially noted that the ratio of the radii of the Fe3+ and Ti4+ cations in the same coordination is determined by the spin state of the first cation. For the tetrahedral coordination, the radius of Fe3+ cation is 0.630 Å, and it for the Ti4+ is 0.560 Å. In tetrahedral coordination, the Fe3+ cation can be only in the HS state. So, the Fe2+ cation in the octahedral coordination in the HS state has an ionic raidius of 0.920 Å, and in the LS state its ionic raidius is 0.750 Å. For the tetrahedral coordination, the radius of Fe2+ cation is 0.770 Å. In the tetrahedral coordination, the Fe2+ cation can be only in the HS state too. In general, we can propose the following mechanism for substitution of iron cations by titanium cations. Up to x = 0.25 concentration, titanium cations substitute the iron cations in 12k and 4fVI octahedral positions. Fe2+ cations also appear in these octahedral positions. This leads to an increase in the a parameter and the V unit cell volume. Above a concentration of 0.25, titanium cations also appear in 4fIV tetrahedral positions, remaining predominantly in octahedral ones. The Fe2+ cations now appear mainly in tetrahedral positions, which leads to a decrease in the a parameter and the V unit cell volume. It is taking into account that the Fe2+ cation in tetrahedral coordination is a Jahn-Teller one, it is easy to understand the continuing increase in the c parameter along with the decrease in the a parameter and the V unit cell volume with increasing substitution level. Considering the fact that the LS state of the Fe2+ cations can be observed, the effect of a decrease in the V unit cell volume can increase. Such substitution model agrees well with the results of magnetic measurements, that will be seen somewhat lower, in which the total magnetic moment of solid solutions constantly decreases with increasing concentration of substitution. However, to establish a reliable distribution of titanium substitutional cations in different crystallographic positions, it is necessary to perform the powder neutron diffraction (NPD) experiments in a wide temperature range. Fig. 3 shows the Mössbauer spectrum of one BaFe12-xTixO19 sample with x = 0.25. It is a superposition of seven sextets and one doublet, corresponding to the nuclei of the Fe3+ and Fe2+ cations, located in magnetically nonequivalent positions. The parameters of sextets and doublets for such positions are shown in Table. 2. As can be seen from Fig. 3 and Table. 2, the change in the parameters of the Mössbauer spectra with respect to the spectrum of BaFe12O19 [54] is already observed at x = 0.25. The S1 and S2 components are sextets and correspond to the 12k octahedral iron position, the S3 corresponds to the 4fVI octahedral position, S4 corresponds to the 4fIV tetrahedral position, S5 corresponds to 2b position in trigonal bipyramid and S6 corresponds to the 2a octahedral position. The most interesting is the S7 component with isomer shift 0.7-0.8 mm/s, which corresponds to Fe2.5+ cations. Otherwise, this state corresponds to the intermediate charge state of iron cations caused by the Fe2+ <=> Fe3+ electron hopping. Unfortunately, concentration of Fe2+ cations can not yet be reliably determined due to electron hopping at room temperature due to the lower ffactor. We believe that Fe2+ cations may be localized at lower temperatures. This is one of the directions for further research on hetero-charged hexaferrites.

In addition, the integral intensity of S1 and S5 sextet lines is significantly reduced. The quadrupole splitting and isomeric shift of the additional S7 sextet, has a value close to the parameters of the S1 sextet. This indicates the localization of the Ti4+ cations in coordination polyhedra having common oxygen anions with the 12k position. Such polyhedra are octahedra 2a and 4fVI, tetrahedron 4fIV, trigonal bipyramid 2b. Selective location of the Ti4+ cations, and a decrease in the intensity of S1 sextet, as well as a smaller magnetic field on the iron cores of the additional S5 sextet, indicate a break in the exchange magnetic coupling Fe5(12k)-O-Fe2(2b) and the formation of the nonequivalent position of the Fe3+ cations of the 12k sublattice denoted like 12k/. The selectivity in the location of the Ti4+ cations is retained in BaFe12-xTixO19 hexaferrites with an increase in the x substitution level. Such localization provides a further decrease in the residual magnetization and coercive force, which is observed in their dependence on the x. Some Raman spectra measured for BaFe12-xTixO19 at room temperature are shown in Fig. 4. In the frequency range of 100-1000 cm-1 for the undoped BaFe12O19, there are twelve peaks at frequencies ν ∼ 172, 183, 213, 282, 318, 343, 412, 469, 520, 616, 686 and 716 cm-1. This is in satisfactory agreement with the well-known results obtained earlier [55]. Modes ν in the range of 318 – 716 cm-1 are mainly associated with oscillations of iron polyhedra. The 343, 469 and 616 cm-1 modes are due to vibrations of the Fe1(2a)-O6 octahedra. The modes 318, 520 and 616 cm-1 are due to vibrations of the Fe4(4fVI)/Ti4(4fVI)-O6 octahedra. The 412, 520 and 616 cm-1 modes are due to vibrations of the Fe5(12k)/Ti5(12k)-O6 octahedra. The 686 cm-1 modes are associated with oscillations of the bipyramidal anion Fe2(2b)-O5sublattices, and the 716 cm-1 modes are associated with oscillations of the tetrahedral anion Fe3(4fIV)/Ti3(4fIV)-O4 sublattices. The contribution of the Ti4+ diamagnetic cations leads to a shift and distortion of the Raman spectra. As can be seen from the spectra, with an increase in the concentration of substituent cations, the modes shift in the field of lower values. Modes 318, 520 and 716 cm-1 are very strongly split, which confirms the proposed model for the substitution of Fe3+ iron cations by Ti4+ titanium ones at the tetrahedral 4fIV and octahedral 4fVI and 12k positions. The results of temperature measurements of the magnetization are shown in Fig. 5. In a strong magnetic field of 1 T, close to the saturation field, a similar behavior of the ZFC and FC curves is observed. They almost coincide. An extended horizontal section is allocated for all the substitution levels. This indicates homogeneous magnetic ordering. In this case it is ferrimagnetic. The magnitude of the magnetization in this field is close to the saturation magnetization. From Fig. 5 it is clearly seen that the magnitude of the magnetization decreases with increasing concentration of substitution at the same fixed temperature. In region of ~35 K, a peak is observed in the ZFC curve. This peak can be explained by the formation of a noncollinear magnetic structure, since the field is too large for cluster behavior [56]. Above this peak temperature, the ZFC curve continues to grow slightly, merging with the FC curve in the limit. A noncollinear magnetic structure can arise, and as a result of a change in the spin state of Fe2+ cations from LS to HS with increasing temperature [57]. This behavior is observed in some iron-organic complexes, where iron cations have a two plus charge [58]. The temperature of divergence of the ZFC and FC curves in a strong field is fixed in the region of ~ 150 K, slightly decreasing with increase in substitution level (Fig. 5). Such a decrease in the divergence temperature indicates a weakening of the exchange between the sublattices with noncollinear ordering. In a weak field, this divergence temperature increases to ~ 200 K. It also decreases with the substitution level. This behavior may indicate that such a noncollinear ordering is due to the deviation from the antiferromagnetic axis of the initially

oppositely directed sublattices of hexaferrite. The formation of this noncollinear ordering may facilitate by the growth of both the substitution level and the external magnetic field. In weak fields the ZFC curves highly likely increase monotonically and do not demonstrate a peak. This also may argue in favor of the formation of a noncollinear magnetic structure and the absence of cluster behavior. Nevertheless, in order to clarify the nature of the magnetic ordering of titansubstituted barium hexaferrites, neutron diffraction studies are required in a wide range of temperatures. Fig. 6 shows the field dependences of the magnetization for the studied series of samples. Curves for all the samples are almost saturated at room temperature already in fields slightly more than 1 T. With increasing the substitution level, the saturation magnetization decreases from ~ 70.6 emu/g to ~ 56.7 emu/g for x = 0.25 and 1, respectively. This corresponds to 1.12 μB and 1.02 μB per Fe2+/3+ iron cation [59]. Fig. 7 shows concentration diagrams of Ms saturation magnetization at room temperature. With increasing the substitution level, Ms decreases monotonically. At x = 0.5, an inflection point is observed. As x increases from 0 to 1, the saturation magnetization decreases from 74.3 emu/g to 56.7 emu/g. This behavior of Ms at room temperature is mainly due to the substitution of paramagnetic Fe3+ iron cations with diamagnetic Ti4+ titanium cations in the dominant 12k crystallographic positions and the appearance of Fe2+ cations with a lower magnetic moment than the Fe3+ cation. Considering the classical ordering of the hexaferrite sublattices by the Gorter model [60], where the spins of Fe2+/3+ iron cations are directed upward for 2a, 2b, and 12k positions and downward for 4fIV and 4fVI positions, the detected magnetic behavior of investigated samples satisfactorily coincides with the above proposed substitution mechanism. As already said, up to x = 0.25 concentration, titanium cations substitute the iron cations in 12k and 4fVI octahedral positions. Fe2+ cations also appear in these octahedral positions. Above a concentration of 0.25, titanium cations also appear in 4fIV tetrahedral positions, remaining predominantly in octahedral ones. Such a substitution leads to a monotonic decrease in the magnetic parameters. Hexaferrites are semiconductors with high value of bandgap. This is due to the features of the chemical bonds Fe3+-O formation. Chemical substitution can change electrical properties of the hexaferrites solid solutions. Increase of the permittivity for samples with diamagnetic substitution (in comparison with pure BaFe12O19) can be due to strong coupling between empty 3d-electronic shells of the diamagnetic ions and oxygen (strong polar bond). Another case is heterovalent substitution. Diamagnetic ions with different oxidation state (not 3+) lead to change of the iron oxidation state. It results in changing of the conductivity mechanism. In pair Fe2+-OFe3+ with mixed iron valence can be observed hoping mechanism (increase of conductivity). Ti ions lead also to appearance of Fe2+ ions. The dielectric properties of the investigated sample with x = 0.5 are presented in Fig. 8. With an increase in the frequency of the alternating current from 104 Hz to 105 Hz, the resistivity at each fixed temperature decreases. The real part of the dielectric constant has value of ~ 0.2 and gradually decreases at heating from room temperature up to ~ 500 K, after which it begins to increase sharply [61]. In the studied frequency range, the real part of the dielectric constant decreases with increasing frequency. The dielectric loss tangent for this sample has a maximum in the region of ~ 500 K and reaches a value of ~ 0.25 at a frequency of 104 Hz. With increasing the frequency, the magnitude of the peak and the temperature position somewhat decrease. With increasing the substitution level, the real part of the dielectric constant and the dielectric loss tangent of all the samples increase. Strong

correlation between chemical composition and electrical properties is the way for control of the functional properties of the hexaferrites. IV. CONCLUSSION The substituted BaFe12-xTixO19 x ≤ 1 polycrystalline samples have been synthesized using the standard solid state sintering method. A non-monotonic change in the parameters of the unit cell is observed. The a parameter has a maximum of 5.896 Å at x = 0.25. Then it decreases almost linearly down to 5.886 Å at x = 1. Rietveld analysis provides a structural model where titanium cations are preferably located in the following positions: 4fIV tetrahedral and octahedral 4fVI and 12k ones. The homogeneous ferrimagnetic ordering is detected by ZFC and FC measurements down to ~ 35 K. Below this temperature the noncollinear magnetic structure can formed as a result of a change in the spin state of Fe2+ cations from HS to LS. The saturation magnetization decreases from ~ 70.6 emu/g to ~ 56.7 emu/g for x = 0.25 and 1, respectively. The ac-resistivity decreases with an increase in the frequency from 104 Hz to 105 Hz for all the samples. With increasing the substitution level, the resistivity of all the samples increases. The real part of the dielectric constant has value of ~ 0.2 for x = 0.5 and gradually decreases at heating from room temperature up to ~ 500 K, after which it begins to increase sharply. The dielectric loss tangent for this sample has a maximum in the region of ~ 500 K and reaches a value of ~ 0.25 at a frequency of 104 Hz. Strong correlation between Ti concentration in hexaferrites, their crystal structure, magnetic and electgrical properties were established. It open broad perspectives for practical applications. Acknowledgment The work was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0011. This work was partially supported by the Ministry of Education and Science of the Russian Federation (Government task in SUSU 4.1346.2017/4.6 and the framework of Increase Competitiveness Program of MISiS P02-2017-2-4) and by the Russian Foundation for Basic Research (№ 18-32-00663, № 19-53-04010) and Belarussian Foundation for Basic Research (№ F19RM-011). Additionally this work was performed using equipment of MIPT Shared Facilities Center and with financial support from the Ministry of Education and Science of the Russian Federation (Grant No. RFMEFI59417X0014).

References 1. M. Gich, I. Fina, A. Morelli, F. Sánchez, M. Alexe, J. Gàzquez, J. Fontcuberta, A. Roig, Multiferroic iron oxide thin films at room temperature, Adv. Mat. 26 (2014) 4645-4652. https://doi.org/10.1002/adma.201400990. 2. V.V. Sereda, D.S. Tsvetkov, I.L. Ivanov, A.Yu. Zuev, Interplay between chemical strain, defects and ordering in Sr1-xLaxFeO3 materials, Acta Mater. 162 (2019) 33-45. https://doi.org/10.1016/j.actamat.2018.09.051. 3. W. Rheinheimer, X. LiPhuah, H. Wang, F. Lemke, M.J. Hoffmann, H. Wang, The role of point defects and defect gradients in flash sintering of perovskite oxides, Acta Mater. 165 (2019) 398-408. https://doi.org/10.1016/j.actamat.2018.12.007. 4. I. Nelson, L. Gardner, K. Carlson, S.E. Naleway, Freeze casting of iron oxide subject to a triaxial nested Helmholtz-coils driven uniform magnetic field for tailored porous scaffolds, Acta Mater. 173 (2019) 106-116. https://doi.org/10.1016/j.actamat.2019.05.003. 5. L. Hou, L. Shi, J. Zhao, S. Zhou, S. Pan, X. Yuan, Y. Xin, Room-temperature multiferroicity in CeFeO3 ceramics, J. Alloys Compd. 797 (2019) 363-369. https://doi.org/10.1016/j.jallcom.2019.05.078. 6. D.I. Tishkevich, I.V. Korolkov, A.L. Kozlovskiy, M. Anisovich, D.A. Vinnik, A.E. Ermekova, A.I. Vorobjova, E.E. Shumskaya, T.I. Zubar, S.V. Trukhanov, M.V. Zdorovets, A.V. Trukhanov, Immobilization of boron-rich compound on Fe3O4 nanoparticles: Stability and cytotoxicity, J. Alloys Compd. 797 (2019) 573-581. https://doi.org/10.1016/j.jallcom.2019.05.075. 7. A.V. Trukhanov, M.A. Almessiere, A. Baykal, S.V. Trukhanov, Y. Slimani, D.A. Vinnik, V.E. Zhivulin, A.Yu. Starikov, D.S. Klygach, M.G. Vakhitov, T.I. Zubar, D.I. Tishkevich, E.L. Trukhanova, M. Zdorovets, Influence of the charge ordering and quantum effects in heterovalent substituted hexaferrites on their microwave characteristics, J. Alloys Compd. 788 (2019) 1193-1202. https://doi.org/10.1016/j.jallcom.2019.02.303. 8. S.V. Trukhanov, A.V. Trukhanov, L.V. Panina, V.G. Kostishyn, V.A. Turchenko, E.L. Trukhanova, An.V. Trukhanov, T.I. Zubar, V.M. Ivanov, D.I. Tishkevich, D.A. Vinnik, S.A. Gudkova, D.S. Klygach, M.G. Vakhitov, P. Thakur, A. Thakur, Y. Yang, Temperature evolution of the structure parameters and exchange interactions in BaFe12-xInxO19, J. Magn. Magn. Mater. 466 (2018) 393-405. https://doi.org/10.1016/j.jmmm.2018.07.041. 9. S.V. Trukhanov, A.V. Trukhanov, V.G. Kostishin, L.V. Panina, I.S. Kazakevich, V.A. Turchenko, V.V. Oleinik, E.S. Yakovenko, L.Y. Matsui, Magnetic and absorbing properties of M-type substituted hexaferrites BaFe12-xGaxO19 (0.1 < x < 1.2), JETP 123 (2016) 461-469. https://doi.org/10.1134/S1063776116090089. 10. A.V. Trukhanov, V.O. Turchenko, I.A. Bobrikov, S.V. Trukhanov, I.S. Kazakevich, A.M. Balagurov, Crystal structure and magnetic properties of the BaFe12-xAlxO19 (x=0.1–1.2) solid solutions, J. Magn. Magn. Mater. 393 (2015) 253-259. https://doi.org/10.1016/j.jmmm.2015.05.076. 11. D.A. Vinnik, A.B. Ustinov, D.A. Zherebtsov, V.V. Vitko, S.A. Gudkova, I. Zakharchuk, E. Lähderanta, R. Niewa, Structural and millimeter-wave characterization of flux grown Al substituted barium hexaferrite single crystals, Ceram. Int. 41 (2015) 12728-12733. https://doi.org/10.1016/j.ceramint.2015.06.105. 12. D.A. Vinnik, I.A. Ustinova, A.B. Ustinov, S.A. Gudkova, D.A. Zherebtsov, E.A. Trofimov, N.S. Zabeivorota, G.G. Mikhailov, R.Niewa, Millimeter-wave characterization of aluminum substituted barium lead hexaferrite single crystals grown from

PbO-B2O3 flux, Ceram. Int. 43 (2017) 15800-15804. https://doi.org/10.1016/j.ceramint.2017.08.145. 13. S.V. Trukhanov, A.V. Trukhanov, V.G. Kostishyn, L.V. Panina, An.V. Trukhanov, V.A. Turchenko, D.I. Tishkevich, E.L. Trukhanova, V.V. Oleynik, O.S. Yakovenko, L.Yu. Matzui, D.A. Vinnik, Magnetic, dielectric and microwave properties of the BaFe12xGaxO19 (x ≤ 1.2) solid solutions at room temperature, J. Magn. Magn. Mater. 442 (2017) 300310. https://doi.org/10.1016/j.jmmm.2017.06.022. 14. H. Sözeri, F. Genç, M.A. Almessiere, İ.S. Ünver, A.D. Korkmaz, A. Baykal, Cr3+substituted Ba nanohexaferrites as high-quality microwave absorber in X band, J. Alloys Compd. 779 (2019) 420-426. https://doi.org/10.1016/j.jallcom.2018.11.309. 15. A.V. Trukhanov, S.V. Trukhanov, V.G. Kostishyn, L.V. Panina, V.V. Korovushkin, V.A. Turchenko, D.A. Vinnik, E.S. Yakovenko, V.V. Zagorodnii, V.L. Launetz, V.V. Oliynyk, T.I. Zubar, D.I. Tishkevich, E.L. Trukhanova, Correlation of the atomic structure, magnetic properties and microwave characteristics in substituted hexagonal ferrites, J. Magn. Magn. Mater. 462 (2018) 127-135. https://doi.org/10.1016/j.jmmm.2018.05.006. 16. S.V. Trukhanov, A.V. Trukhanov, V.G. Kostishyn, L.V. Panina, An.V. Trukhanov, V.A. Turchenko, D.I. Tishkevich, E.L. Trukhanova, O.S. Yakovenko, L.Yu. Matzui, D.A. Vinnik, D.V. Karpinsky, Effect of gallium doping on electromagnetic properties of barium hexaferrite, J. Phys. Chem. Sol. 111 (2017) 142-152. https://doi.org/10.1016/j.jpcs.2017.07.014. 17. V.G. Kostishyn, L.V. Panina, А.V. Timofeev, L.V. Kozhitov, A.N. Kovalev, A.K. Zyuzin, Dual ferroic properties of hexagonal ferrite ceramics BaFe12O19 and SrFe12O19 J. Magn. Magn. Mater. 400 (2016) 327-332. https://doi.org/10.1016/j.jmmm.2015.09.011. 18. S.V. Trukhanov, A.V. Trukhanov, V.G. Kostishin, L.V. Panina, I.S. Kazakevich, V.A. Turchenko, V.V. Kochervinskiy, Coexistence of spontaneous polarization and magnetization in substituted M-type hexaferrites BaFe12–xAlxO19 (x ≤ 1.2) at room temperature, JETP Lett. 103 (2016) 100-105. https://doi.org/10.1134/S0021364016020132. 19. A.V. Trukhanov, S.V. Trukhanov, L.V. Panina, V.G. Kostishyn, D.N. Chitanov, I.S. Kazakevich, A.V. Trukhanov, V.A. Turchenko, Strong corelation between magnetic and electrical subsystems in diamagnetically substituted hexaferrites ceramics, Ceram. Int. 43 (2017) 5635-5641. https://doi.org/10.1016/j.ceramint.2017.01.096. 20. A.V. Trukhanov, S.V. Trukhanov, V.G. Kostishin, L.V. Panina, M.M. Salem, I.S. Kazakevich, V.A. Turchenko, V.V. Kochervinskii, D.A. Krivchenya, Multiferroic properties and structural features of M-type Al-substituted barium hexaferrites, Phys. Solid State 59 (2017) 737-745. https://doi.org/10.1134/S1063783417040308. 21. A.V. Trukhanov, S.V. Trukhanov, L.V. Panina, V.G. Kostishyn, I.S. Kazakevich, An.V. Trukhanov, E.L. Trukhanova, V.O. Natarov, V.A. Turchenko, M.M. Salem, A.M. Balagurov, Evolution of structure and magnetic properties for BaFe11.9Al0.1O19 hexaferrite in a wide temperature range, J. Magn. Magn. Mater. 426 (2017) 487-496. https://doi.org/10.1016/j.jmmm.2016.10.140. 22. S.V. Trukhanov, A.V. Trukhanov, V.A. Turchenko, An.V. Trukhanov, D.I. Tishkevich, E.L. Trukhanova, T.I. Zubar, D.V. Karpinsky, V.G. Kostishyn, L.V. Panina, D.A. Vinnik, S.A. Gudkova, E.A. Trofimov, P. Thakur, A. Thakur, Y. Yang, Magnetic and dipole moments in indium doped barium hexaferrites, J. Magn. Magn. Mater. 457 (2018) 83-96. https://doi.org/10.1016/j.jmmm.2018.02.078.

23. V. Turchenko, A. Trukhanov, S. Trukhanov, M. Balasoiu, N. Lupu, Correlation of crystalline and magnetic structures of barium ferrites with dual ferroic properties, J. Magn. Magn. Mater. 477 (2019) 9-16. https://doi.org/10.1016/j.jmmm.2018.12.101. 24. J. Kreisel, H. Vincent, F. Tasset, M. Paté, J.P. Ganne, An investigation of the magnetic anisotropy change in BaFe12-2xTixCoxO19 single crystals, J. Magn. Magn. Mater. (2001) 17-29. https://doi.org/10.1016/S0304-8853(00)01355-X. 25. C.L. Dube, S.C. Kashyap, D.K. Pandya, D.C. Dube, Dieletric and magnetic properties of Zn-Ti substituted M-type barium hexaferrite, Phys. Status Solidi A 206 (2009) 2627-2631. https://doi.org/10.1002/pssa.200925104. 26. A. Davoodi, B. Hashemi, Magnetic properties of Sn–Mg substituted strontium hexaferrite nanoparticles synthesized via coprecipitation method, J. Alloys Compd. 509 (2011) 58935896. https://doi.org/10.1016/j.jallcom.2011.03.002. 27. M.N. Ashiq, R.B. Qureshi, M.A. Malana, M.F. Ehsan, Synthesis, structural, magnetic and dielectric properties of zirconium copper doped M-type calcium strontium hexaferrites, J. Alloys Compd. 617 (2014) 437-443. http://dx.doi.org/10.1016/j.jallcom.2014.08.015. 28. C. Liu, Y. Zhang, J. Jia, Q. Sui, N. Ma, P. Du, Multi-susceptibile single-phased ceramics with both considerable magnetic and dielectric properties by selectively doping, Sci. Rep. 5 (2015) 9498-7. https://doi.org/10.1038/srep09498. 29. M. Waqar, M.A. Rafq, T.A. Mirza, F.A. Khalid, A. Khaliq, M.S. Anwar, M. Saleem, Synthesis and properties of nickel-doped nanocrystalline barium hexaferrite ceramic materials, Appl. Phys. A 124 (2018) 286-7. https://doi.org/10.1007/s00339-018-1717-z. 30. M.A. Almessierea, Y. Slimani, H.S. El Sayed, A. Baykal, I. Ercan, Microstructural and magnetic investigation of vanadium-substituted Sr nanohexaferrite, J. Magn. Magn. Mater. 471 (2019) 124–132. https://doi.org/10.1016/j.jmmm.2018.09.054. 31. P.D. Battle, T.C. Gibb, P. Lightfoot, The structural consequences of charge disproportionation in mixed-valence iron oxides. I. The crystal structure of Sr2LaFe3O8.94 at room temperature and 50 K, J. Solid State Chem. 84 (1990) 271-279. https://doi.org/10.1016/0022-4596(90)90325-R. 32. W. Zhang, Y. Bai, X. Han, L. Wang, X. Lu, L. Qiao, Magnetic properties of Co-Ti substituted barium hexaferrite, J. Alloys Compd. 546 (2013) 234-238. https://doi.org/10.1016/j.jallcom.2012.08.029. 33. L. Wang, H. Yu, X. Ren, G. Xu, Magnetic and microwave absorption properties of BaMnxCo1−xTiFe10O19, J. Alloys Compd. 588 (2014) 212-216. https://doi.org/10.1016/j.jallcom.2013.11.072. 34. P. Meng, K. Xiong, L. Wang, S. Li, Y. Cheng, G. Xu, Tunable complex permeability and enhanced microwave absorption properties of BaNixCo1-xTiFe10O19, J. Alloys Compd. 628 (2015) 75-80. https://doi.org/10.1016/j.jallcom.2014.10.163. 35. S. Verma, O.P. Pandey, A. Paesano Jr., P. Sharma, Structural and magnetic properties of Co-Ti substituted barium hexaferrite thick films, J. Alloys Compd. 678 (2016) 284-289. https://doi.org/10.1016/j.jallcom.2016.03.283. 36. J. Chen, P. Meng, M. Wang, G. Zhou, X. Wang, G. Xu, Electromagnetic and microwave absorption properties of BaMgxCo1-xTiFe10O19, J. Alloys Compd. 679 (2016) 335-340. https://doi.org/10.1016/j.jallcom.2016.04.001. 37. D.S. Klygach, M.G. Vakhitov, D.A. Vinnik, A.V. Bezborodov, S.A. Gudkova, V.E. Zhivulin, D.A. Zherebtsov, C.P. SakthiDharana, S.V. Trukhanov, A.V. Trukhanov,

A.Yu. Starikova, Measurement of permittivity and permeability of barium hexaferrite, J. Magn. Magn. Mat. 465 (2018) 290-294. https://doi.org/10.1016/j.jmmm.2018.05.054. 38. D.A. Vinnik, D.S. Klygach, V.E. Zhivulin, A.I. Malkin, M.G. Vakhitov, S.A. Gudkova, D.M. Galimov, D.A. Zherebtsov, E.A. Trofimov, N.S. Knyazev, V.V. Atuchin, S.V. Trukhanov, A.V. Trukhanov, Electromagnetic properties of BaFe12O19:Ti at centimeter wavelengths, J. Alloys Compd. 755 (2018) 177-183. https://doi.org/10.1016/j.jallcom.2018.04.315. 39. V.A. Zhuravlev, V.I. Itin, R.V. Minin, Yu.M. Lopushnyak, V.A. Svetlichnyi, I.N. Lapin, D.A. Velikanov, I.Yu. Lilenko, Influence of different organic fuels on the phase composition, structure parameters and magnetic properties of hexaferrites BaFe12O19 synthesized by the sol-gel combustion, J. Alloys Compd. 771 (2019) 686-698. https://doi.org/10.1016/j.jallcom.2018.08.294. 40. C. Liu, Y. Zhang, Y. Zhang, G. Fang, X. Zhao, K. Peng, J. Zou, Multiple nature resonance behavior of BaFexTiO19 controlled by Fe/Ba ratio and its regulation on microwave absorption properties, J. Alloys Compd. 773 (2019) 730-738. https://doi.org/10.1016/j.jallcom.2018.09.278. 41. P. Gütlich, A. Hauser, H. Spiering, Thermal and optical switching of Iron(II) complexes , Angew. Chem. Int. Ed. Engl. 33 (1994) 2024-2054. https://doi.org/10.1002/anie.199420241. 42. S.V. Trukhanov, A.V. Trukhanov, V.A. Turchenko, V.G. Kostishyn, L.V. Panina, I.S. Kazakevich, A.M. Balagurov, Structure and magnetic properties of BaFe11.9In0.1O19 hexaferrite in a wide temperature range, J. Alloys Compd. 689 (2016) 383-393. https://doi.org/10.1016/j.jallcom.2016.07.309. 43. V.A. Turchenko, A.V. Trukhanov, I.A. Bobrikov, S.V. Trukhanov, A.M. Balagurov, Study of the crystalline and magnetic structures of BaFe11.4Al0.6O19 in a wide temperature range, J. Surf. Investig. 9 (2015) 17-23. https://doi.org/10.1134/S1027451015010176. 44. T. Degen, M. Sadki, E. Bron, U. König, G. Nénert, The HighScore suite, Powder Diffraction 29 (2014) S13-S18. https://doi.org/10.1017/S0885715614000840. 45. http://www.icdd.com/ 46. H.M. Rietveld, A profile refinement method for nuclear and magnetic structures, J. Appl. Cryst. 2 (1969) 65-71. https://doi.org/10.1107/s0021889869006558. 47. J. Rodriguez-Carvajal, Recent advances in magnetic structure determination by neutron powder diffraction, Phys. B 192 (1993) 55-69. https://doi.org/10.1016/0921-4526(93)90108-i. 48. T. Kmjec, M. Adamec, D. Kubaniova, J. Plocek, M. Dopita, M. Cesnek, V. Chlana, J. Bednarcik, K. Zaveta, M. Marysko, J. Kohout, 57Fe-enriched perovskites M(Fe0.5Nb0.5)O3 (M – Pb, Ba) studied by Mössbauer spectroscopy, NMR and XRD in the wide temperature range 4.2-533 K, J. Magn. Magn. Mater. 475 (2019) 334-344. https://doi.org/10.1016/j.jmmm.2018.11.087. 49. N. Mironova-Ulmane, A. Kuzmin, M. Grube, Raman and infrared spectromicroscopy of manganese oxides, J. Alloys Compd. 480 (2009) 97-99. https://doi.org/10.1016/j.jallcom.2008.10.056. 50. S.V. Trukhanov, A.V. Trukhanov, A.N. Vasiliev, H. Szymczak, Frustrated exchange interactions formation at low temperatures and high hydrostatic pressures in La0.70Sr0.30MnO2.85, JETP 111 (2010) 209-214. https://doi.org/10.1134/S106377611008008X. 51. S.V. Trukhanov, A.V. Trukhanov, A.N. Vasiliev, A.M. Balagurov, H. Szymczak, Magnetic state of the structural separated anion-deficient La0.70Sr0.30MnO2.85 manganite. JETP 113 (2011) 819-825. https://doi.org/10.1134/S1063776111130127.

52. S.V. Trukhanov, A.V. Trukhanov, M.M. Salem, E.L. Trukhanova, L.V. Panina, V.G. Kostishyn, M.A. Darwish, An.V. Trukhanov, T.I. Zubar, D.I. Tishkevich, V. Sivakov, D.A. Vinnik, S.A. Gudkova, Charanjeet Singh, Preparation and investigation of structure, magnetic and dielectric properties of (BaFe11.9Al0.1O19)1-x - (BaTiO3)x bicomponent ceramics, Ceram. Int. 44 (2018) 21295-21302. https://doi.org/10.1016/j.ceramint.2018.08.180. 53. R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Crystallogr. A 32 (1976) 751-767. https://doi.org/10.1107/s0567739476001551. 54. A.V. Trukhanov, V.G. Kostishyn, L.V. Panina, S.H. Jabarov, V.V. Korovushkin, S.V. Trukhanov, E.L. Trukhanova, Magnetic properties and Mössbauer study of gallium doped M-type barium hexaferrites, Ceram. Int. 43 (2017) 12822–12827. http://dx.doi.org/10.1016/j.ceramint.2017.06.172. 55. A.V. Trukhanov, N.T. Dang, S.V. Trukhanov, S.H. Jabarov, I.S. Kazakevich, A.I. Mammadov, R.Z. Mekhdiyeva, V.A. Turchenko, R.E. Huseynov, Crystal structure, magnetic properties, and raman spectra of solid solutions BaFe12–xAlxO19, Phys. Solid State 58 (2016) 992-996. https://doi.org/10.1134/S1063783416050267. 56. I.O. Troyanchuk, S.V. Trukhanov, D.D. Khalyavin, H. Szymczak, Magnetic properties of anion deficit manganites Ln0.55Ba0.45MnO3-γ (Ln=La, Nd, Sm, Gd, γ⩽0.37), J. Magn. Magn. Mater. 208 (2000) 217-220. https://doi.org/10.1016/S0304-8853(99)00529-6. 57. N. Paradis, G. Chastanet, J.‐F. Létard, When stable and metastable HS states meet in spin‐crossover compounds, Eur. J. Inorg. Chem. 2012 (2012) 3618-3624. https://doi.org/10.1002/ejic.201200297. 58. N. Paradis, G. Chastanet, T. Palamarciuc, P. Rosa, F. Varret, K. Boukheddaden, J.-F. Létard, Detailed investigation of the interplay between the thermal decay of the low temperature metastable HS state and the thermal hysteresis of spin-crossover solids, J. Phys. Chem. C 119 (2015) 20039-20050. https://doi.org/10.1021/acs.jpcc.5b03680. 59. A.V. Trukhanov, M.A. Darwish, L.V. Panina, A.T. Morchenko, V.G. Kostishyn, V.A. Turchenko, D.A. Vinnik, E.L. Trukhanova, K.A. Astapovich, A.L. Kozlovskiy, M. Zdorovets, S.V. Trukhanov, Features of crystal and magnetic structure of the BaFe12xGaxO19 (x ≤ 2) in the wіde temperature range, J. Alloys Compd. 791 (2019) 522-529. https://doi.org/10.1016/j.jallcom.2019.03.314. 60. E.W. Gorter, Some properties of ferrites in connection with their chemistry, Proc. IRE 43 (1955) 1945-1973. https://doi.org/10.1109/jrproc.1955.278060. 61. S.V. Trukhanov, A.V. Trukhanov, V.G. Kostishyn, L.V. Panina, An.V. Trukhanov, V.A. Turchenko, D.I. Tishkevich, E.L. Trukhanova, O.S. Yakovenko, L.Yu. Matzui, Investigation into the structural features and microwave absorption of doped barium hexaferrites, Dalton Trans. 46 (2017) 9010-9021. https://doi.org/10.1039/c7dt01708a.

Table. 1. Unit cell parameters, cation coordinates and standart reliability factors for the solid solutions of BaFe12-xTixO19 x = 0 and 0.75 hexaferrites at 300 K in frame of SG P63/mmc (No 194) obtained by Rietveld method in Fullprof compute program. Common cation coordinates are : Ba (2d) (2/3, 1/3, 1/4), (Fe/Ti)1 (2a) (0, 0, 0); (Fe/Ti)2 (2b) (0, 0, 1/4); (Fe/Ti)3 (4fIV*) (1/3, 2/3, z); (Fe/Ti)4 (4fVI*) (1/3, 2/3, z); (Fe/Ti)5 (12k) (x, 2x, z); O1 (4e) (0, 0, z); O2 (4f) (1/3, 2/3, z); O3 (6h) (x, 2x, 1/4); O4 (12k) (x, 2x, z); O5 (12k) (x, 2x, z). *fIV – tetrahedral oxygen coordination, *fVI – octahedral oxygen coordination. x No

Crystal structure parameters 0

0.75

a, (Å)

5.8961(2)

5.8898(12)

c, (Å)

23.2154(7)

23.2675(4)

3.

V, (Å3)

698.94(3)

699.01(2)

4.

Fe3/Ti3 (4fIV), z

0.0256(5)

0.0268(3)

5.

Fe4/Ti4 (4fVI), z

0.1909(5)

0.1885(3)

6.

Fe5/Ti5 (12k), x

0.1648(2)

0.1679(12)

7.

Fe5/Ti5 (12k), z

0.6082(2)

0.6082(14)

8.

O1 (4e), z

0.1357(19)

0.1551(13)

O2 (4f), z

0.5555(2)

0.5562(9)

10.

O3 (6h), x

0.1743(8)

0.1813(5)

11.

O4 (12k), x

0.1533(5)

0.1562(3)

12.

O4 (12k), z

0.05304(8)

0.05495(5)

13.

O5 (12k), x

0.5163(5)

0.5077(2)

14.

O5 (12k), z

0.1269(2)

0.1534(6)

15.

Rwp, %

27.1

19.6

Rexp, %

20.07

13.38

RB, %

9.28

7.77

χ2

1.82

2.14

1. 2.

9.

16. 17. 18.

unit cell parameters

cation coordinates

reliability factors

Table. 2. Evaluated data of Mössbauer spectrum of the BaFe11.75Ti0.25O19 at room temperature. S is 6-line-component and D is 2-line-component.

No

Component

1.

S1

2.

S2

3.

S3

4.

S4

5.

S5

6.

S6

7.

S7

8.

S

9.

D1

10.

D

Area fraction of total

Area fraction of component

Isomer shift [mm/s]

Quadrupole shift/splitting [mm/s]

Hyperfine induction [T]

0.343± 0.009 0.154± 0.011 0.149± 0.012 0.162± 0.008 0.072± 0.004 0.096± 0.015 0.020± 0.002 0.996± 0.001 0.0040± 0.0010 0.004± 0.001

0.344± 0.009 0.155± 0.011 0.150± 0.012 0.163± 0.008 0.072± 0.004 0.096± 0.015 0.020± 0.002

0.351± 0.001 0.299± 0.018 0.374± 0.003 0.255± 0.004 0.231± 0.011 0.342± 0.007 0.793± 0.021

0.408± 0.003 0.154± 0.038 0.195± 0.011 0.221± 0.006 2.041± 0.019 0.062± 0.017 1.542± 0.037

41.44± 0.01 40.26± 0.17 51.15± 0.03 48.56± 0.04 39.82± 0.09 49.78± 0.17 28.85± 0.18 44.31± 0.15

Mean hyperfine induction

Area ratio line 2 to 1

Area ratio line 3 to 1

Distribution width [mm/s]

Linewidth 1 (and 6) [mm/s]

0.692± 0.004 0.692± 0.004 0.692± 0.004 0.692± 0.004 0.692± 0.004 0.692± 0.004 0.692± 0.004

0.353± 0.003 0.353± 0.003 0.353± 0.003 0.353± 0.003 0.353± 0.003 0.353± 0.003 0.353± 0.003

0.052± 0.006 0.965± 0.062 0.000± 0.020 0.053± 0.014 0.255± 0.027 0.116± 0.054 0.060± 0.000

0.294± 0.005 0.294± 0.005 0.294± 0.005 0.294± 0.005 0.294± 0.005 0.294± 0.005 0.294± 0.005

-

-

-

-

1.000± 0.000

0.115± 0.079

0.474± 0.132

-

1.000± 0.000

-

-

0.290± 0.000

-

-

-

-

-

-

-

-

Figure captions Fig. 1. XRD patterns of BaFe12-xTixO19 with x = 0 and 0.75 at room temperature. The diffraction data was processed by the Rietveld method in FullProf program. Crosses represent experimental points. The upper curve represents the fitting spectrum. The lower curve represents the difference between the experimental and fitting data. The bar set defines the angular positions of the Bragg peaks. Fig. 2. Dependence of unit cell parameters a (a), c (b) and cell volume (c) vs. x at room temperature for BaFe12-xTixO19. Fig. 3. Mössbauer spectrum at room temperature for BaFe12-xTixO19 with x = 0.25. Fig. 4. Raman spectra at room temperature for BaFe12-xTixO19 with x = 0 (a), 0.5 (b). Fig. 5. Temperature dependence of ZFC (full symbols) and FC (open symbols) magnetization curves in field of 1 T for BaFe12-xTixO19 with x = 0.25 (circle) and 1 (rectangle). Fig. 6. Field dependences of magnetization at room temperature (a) and at 5 K (b) for BaFe12xTixO19 with x =0; 0.25; 0.5; 0.75 and 1. Fig. 7. Concentrational dependence of saturation magnetization at room temperature for BaFe12xTixO19. Fig. 8. Temperature dependence of real part of permittivity (a) and loss tangent (b) at frequencies of 104 Hz (open rectangle) and 105 Hz (open rectangle) for BaFe12-xTixO19 with x = 0.5. Insert demonstrate temperature dependence of loss tangent on an enlarged scale.

4

I ( arb. un. )

3

a

BaFe 12-xTixO 19

T=300K

x=0

2 1 0 -1

b

9

I ( arb. un. )

T=300K

BaFe 12-xTixO 19

6

x = 0.75

3

0

-3 20

40

2  ( deg )

Fig. 1

60

80

a(A)

5,896

a

a 5,892

T=300K

5,888

23,28

c(A)

b

23,25

T=300K

c 23,22 699,5

3

V(A )

c

699,0

V T=300K 698,5

0,0

0,2

0,4

0,6

x

Fig. 2

0,8

1,0

Fig. 3

a

686

x=0

4

616

I ( arb. un. )

2

183 172

213

318 343 412 469 520

716

282

0 1,5

b

x=0.5

682

1,0 713

313 609

522

0,5 166 205

0,0

200

409 464

400

600 -1

 ( cm )

Fig. 4

800

70

FC ZFC

M ( emu/g )

68 x=0.25

60

x=0.25

67 0

FC

50

55

ZFC

50 54

0

0

x=1.00

x=1.00

B=1 T

50

100

200

T(K)

Fig. 5

300

60

M ( emu/g )

T=300K 30

BaFe12-xTixO19

0

x=0 x = 0.25 x = 0.50 x = 0.75 x = 1.00

-30

-60

0

2

a 4

6

B(T)

M ( emu/g )

80

BaFe12-xTixO19

40

T=5K 0

x=0 x = 0.25 x = 0.50 x = 0.75 x = 1.00

-40

b

-80 0

4

2

B(T)

Fig. 6

6

BaFe12-xTi xO19

Ms ( emu/g )

72

66

60

T=300K

0,0

0,2

0,4

0,6

x

Fig. 7

0,8

1,0

8

4

10 Hz

a

BaFe 11.5Ti0.5O 19

4

5

10 Hz

/

 ( arb. un. )

6

2

0

b

4

10 Hz

4

10 Hz 0,2

0,2 0,1 5

tg( )

10 Hz

0,1

0,0

450

500

550

BaFe 11.5Ti0.5O 19

5

10 Hz

0,0 300

400

500

600

700

800

T(K)

Fig. 8 Titanium substitution influence on structure and properties of barium BaFe12-xTixO19 (x ≤ 1) hexaferrites polycrystalline ceramics was investigated. Substitution model by titanium cations was defined. Mossbauer and Raman spectrometry was established. The saturation magnetization decreasing with substitution level increasing was shown. Dielectric constant and dielectric loss tangent values and temperature dependence were measured.