- Email: [email protected]
Antiferromagnetic order in tetragonal bismuth ferrite–lead titanate
Journal of Magnetism and Magnetic Materials 323 (2011) 2533–2535
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Letter to the Editor
Antiferromagnetic order in tetragonal bismuth ferrite–lead titanate Tim P. Comyn a,n, Tim Stevenson a, Maisoon Al-Jawad b, Gilles Andre´ c, Andrew J. Bell a, Robert Cywinski d a
Institute for Materials Research, University of Leeds, Leeds LS2 9JT, UK Centre for Oral Growth and Development, Dental Physical Sciences Group, Queen Mary, University of London, London E1 4NS, UK Laboratoire Le´on Brillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France d School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH, UK b c
a r t i c l e i n f o
abstract
Article history: Received 3 December 2010 Received in revised form 10 March 2011 Available online 13 June 2011
Neutron powder diffraction of particulates of 0.7BiFeO3–0.3PbTiO3 in the tetragonal P4mm phase has been used to determine the type of antiferromagnetic order that occurs below 220 K. It is shown that G-type antiferromagnetic ordering occurs, with magnetic propagation along the 12 12 12 direction. Unlike the rhombohedral R3c phase the direction of antiferromagnetic propagation and the ferroelectric order parameter are not parallel in the tetragonal phase, but at an angle of 49.91. The ground state (at 4 K) magnetic moment is 4.1 mB. & 2011 Elsevier B.V. All rights reserved.
Keywords: Bismuth ferrite Multiferroic Neutron diffraction Antiferromagnetic Ferroelectric Tetragonal
1. Introduction Bismuth ferrite, BiFeO3, is one of the few known roomtemperature multiferroics, displaying both G-type antiferromagnetic and ferroelectric order [1]. It readily forms a solid solution with ferroelectric PbTiO3, resulting in the system xBiFeO3 (1x)PbTiO3, which is also multiferroic at room temperature [2–8] for a wide range of x. Single phase perovskite is more easily achievable in the solid solution than in BiFeO3 [9], whilst DC resistivity values and electric-field induced strains are of the same order as one would expect for undoped lead zirconate titanate (PZT) [10]. We have shown previously that for 0.7BiFeO3–0.3PbTiO3, which is close to the R3c–P4mm phase boundary, the crystallographic phase content is form dependent [11]. Particulate material has a predominantly tetragonal perovskite structure (P4mm) and is paramagnetic at room temperature, as determined using neutron diffraction, whereas dense ceramics are predominantly rhombohedral and display antiferromagnetic order under ambient conditions. Zhu et al. [6] have confirmed the existence of antiferromagnetic order for tetragonal compositions in the range 0.45ox o0.69 using zero-field cooling with SQUID (superconducting quantum interference device) measurements at sub-ambient temperatures. For the composition x¼0.69, a Ne´el temperature of 220 K was recorded.
The identity and magnetic structure of this low temperature tetragonal perovskite antiferromagnetic phase are unknown. There are a number of reported primitive tetragonal perovskites in which magnetic ordering occurs: PbVO3 (P4mm) shows two-dimensional antiferromagnetic order below 43 K [12], plus the observation of either spin-glass or G-type antiferromagnetic order in thin film form [13]; BiCoO3 (P4mm) is a C-type antiferromagnetic with a Ne´el temperature of 470 K [14]; 0.5PbFeO2F–0.5PbTiO3 (P4mm) shows G-type antiferromagnetic order with a Ne´el temperature of 450 K, and a propagation vector k ¼ 12 12 12 [15]. Although 0.5PbFeO2F–0.5PbTiO3 displays the same space group as tetragonal 0.7BiFeO3–0.3PbTiO3, the spontaneous strain or tetragonality (c a)/a is very different. At room temperature and at 4 K, the spontaneous strain of 0.5PbFeO2F–0.5PbTiO3 is extremely low, ca. 0.2%—splitting of the 001/100 peaks in the diffraction data is not evident; 0.7BiFeO3–0.3PbTiO3, however, shows a colossal spontaneous strain of ca. 19% [4], two orders of magnitude larger. The objective of the work reported here was to solve the structure of the antiferromagnetic tetragonal phase of 0.7BiFeO3– 0.3PbTiO3 as a function of temperature, and determine the magnetic ground state. Differences in magnetic structure will be sought with the rhombohedral BiFeO3 end member.
2. Experimental n
Corresponding author. Tel.: þ44 113 3432540; fax: þ44 113 3432384. E-mail address: [email protected] (T.P. Comyn).
0304-8853/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2011.06.009
The powders were formed by rapidly cooling dense ceramic bodies, leading to disintegration as reported previously, generating
2534
T.P. Comyn et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 2533–2535
a predominantly tetragonal material [11]. Neutron diffraction data were gathered using G4.1, a reactor neutron facility at Laboratoire Le´on Brillouin (LLB), France. The powder samples were loaded into vanadium cans, and measurements were taken at room temperature, at 4 K, then upon continuous heating back to room temperature; each temperature point presented is the average of a temperature range of ca. 20 K. Typical collection times were of the order of 40 min per temperature point. A wavelength of 2.4226 A˚ was used. Rietveld refinements were performed using GSAS [16] in order to validate the proposed structural and magnetic models. The magnetic structure was separated from the nuclear lattice in order to alleviate the constraints imposed by the P4mm symmetry. The lattice constants of the magnetic model, containing only magnetic contributions from Fe3 þ with an occupancy of x¼0.7 (akin to 0.7BiFeO3–0.3PbTiO3), were constrained to that of the nuclear structure. The room temperature structural model previously reported was used as a precursor.
Fig. 2. Structural and magnetic refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K; the zoomed region clearly shows the magnetic peaks, which are absent at room temperature.
3. Results and discussion Fig. 1 and Table 1 show the data collected at 4 K, along with refinement and residual. In order to generate a satisfactory fit, it was necessary to generate a large magnetic super-cell containing eight Fe3 þ ions with an occupancy of 0.7 per site, akin to the nuclear phase, with lattice constants a and c double that of the nuclear tetragonal model. Fig. 2 shows an enlarged region of Fig. 1 displaying magnetic Bragg peaks at 30.41 and 54.91, which are absent in data collected at room temperature. These peaks are assigned the labels 12 12 12M and 12 12 32M, respectively. In constructing the magnetic model a number of different scenarios for the spin directions were trialed in order to determine the magnetic moment vector, but due to the dominance of the nuclear model similar refinement residuals were obtained in
Fig. 3. Structure of 0.7BiFeO3–PbTiO3. Only Bi (white), Fe (blue, with arrows), and O (red) are shown. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 1. Structural and magnetic refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K.
Table 1 Results of structural and magnetic Rietveld refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K. Composition
0.7BiFeO3–0.3PbTiO3, 4 K
Phase Weight fraction Moment per Fe3 þ (mB) ˚ Lattice parameters (A)
R3c 0.09(2) 0 a¼ 5.57(1) c ¼13.8(5) Rp ¼7.2, Rwp ¼ 5.2
Residuals (%)
P4mm 0.90(8) 4.1(0) a¼3.805(5) c¼ 4.525(1)
each case. The model generated, with the moments parallel to the propagation vector k ¼ 12 12 12 is shown in Fig. 3. An excellent fit is achieved between the data and the model employing G-type antiferromagnetic order along the 111 direction for the P4mm phase, suggesting a similar structure to 0.5PbFeO2F–0.5PbTiO3, ˚ c¼3.982, (ca)/ which has a low tetragonal distortion (a¼3.974 A, a¼0.2%, and moment per Fe3 þ ¼3.5 mB at 4 K) and magnetic propagation vector k ¼ 12 12 12 . Clearly the tetragonal distortion in this system is far higher, (c a)/a¼18.9% at 4 K. The nuclear and magnetic model generated shows that, unlike in the R3c phase, the antiferromagnetic propagation direction is not aligned with the ferroelectric order parameter but, as depicted in Fig. 4, differs by 49.91. This is contrary to that observed in rhombohedral BiFeO3 [17] and 0.9BiFeO3–0.1PbTiO3 [18], where the polar direction lies in the plane of the magnetic cycloid. It is assumed that the same is also true for other BiFeO3based R3c materials such as 0.7BiFeO3–0.3PbTiO3 prepared in dense ceramic form. However, with the present analysis, it was not possible to determine the absolute direction of magnetic moments, to clarify whether they are parallel to the ferroelectric order parameter (0 0 1) or not.
T.P. Comyn et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 2533–2535
Fig. 4. Primitive unit cell for 0.7BiFeO3–0.3PbTiO3. In the rhombohedral phase (R3c) the antiferromagnetic and ferroelectric ordering directions are aligned, whereas in the tetragonal phase (P4mm) they are not.
2535
Using a combination of P4mm and R3c nuclear phases, and the model constructed at 4 K as a starting point, refinements were performed as a function of temperature. The concentration of the R3c phase was found to be 10.571.5 wt%, and was independent of temperature, providing an indication of a temperature independent phase boundary. The refined moment as a function of temperature is shown in Fig. 6. The Ne´el temperature as reported by Zhu et al. for the similar composition 0.69BiFeO3–0.31PbTiO3 is marked in the figure as a dashed vertical line (220 K); the data presented here suggests a Ne´el temperature in good agreement with this. Above 220 K non-zero values are obtained from the refinement, suggesting considerable short range order; the errors from the refinement are also large at this point.
4. Conclusions The tetragonal phase that exists in 0.7BiFeO3–0.3PbTiO3 displays G-type antiferromagnetic ordering below ca. 220 K. At 4 K, the magnetic moment is 4.1 mB. Contrary to observations in the rhombohedral R3c phase in BiFeO3 and 0.9BiFeO3–0.1PbTiO3, the ferroelectric order parameter and direction of antiferromagnetic propagation in the tetragonal phase are misaligned by 49.91. The structure is similar to that reported for the composition 0.5PbFeO2F–0.5PbTiO3.
Acknowledgments
Fig. 5. Neutron powder diffraction data collected on G4.1 (LLB) and HRPD (ISIS). The inset shows the 32 12 12 peak, visible using HRPD. The model generated here fits well with this data.
The authors gratefully acknowledge Aziz Daoud-Aladine and the Science and Technology Facilities Council, for the data collected on HRPD. References
Fig. 6. Refined magnetic moment for tetragonal 0.7BiFeO3–0.3PbTiO3 as a function of temperature.
The G-type P4mm refinement predicts the presence of a peak ˚ However, this cannot be observed using the resolution at 2.329 A. of G4.1. Fig. 5 shows a combination of the data collected using G4.1 at LLB at 4 K plus data from HRPD at ISIS at 7.5 K (STFC, Didcot, UK), as reported previously [19]. The 32 12 12 reflection can be clearly seen in the inset; here the data are shown as crosses (a number of crosses are omitted to improve clarity) and the refinement is shown as a solid line. Note that in Fig. 5, d-spacing rather than 2y is used on the abscissa.
[1] P. Fisher, M. Polomska, I. Sosnowska, M. Szyman´ski, J. Phys. C 13 (1980) 1931. [2] R.T. Smith, G.D. Achenbach, R. Gerson, W.J. James, J. Appl. Phys. 39 (1) (1968) 70. [3] S.A. Fedulov, P.B. Ladyzhinskii, I.L. Pyatigorskaya, Y.N. Venevtsev, Sov. Phys.—Solid State 6 (2) (1964) 375. [4] V.V.S.S. Sai Sunder, A. Halliyal, A.M. Umarji, J. Mater. Res. 10 (1995) 1301. [5] D.I. Woodward, I.M. Reaney, R.E. Eitel, C.A. Randall, J. Appl. Phys. 94 (5) (2003) 3313. [6] W.-M. Zhu, H.-Y. Guo, Z.-G. Ye, Phys. Rev. B 78 (2008) 014401. [7] S. Bhattacharjee, D. Pandey, J. Appl. Phys. 107 (2010) 124112. [8] R. Ranjan, K.A. Raju, Phys. Rev. B 82 (2010) 054119. [9] T.P. Comyn, S.P. McBride, A.J. Bell, Mater. Lett. 58 (2004) 3844. [10] T.P. Comyn, T. Stevenson, A.J. Bell, J. Phys. IV 128 (2005) 13. [11] T.P. Comyn, T. Stevenson, M. Al-Jawad, S.L. Turner, R.I. Smith, W.G. Marshall, A.J. Bell, R. Cywinski, Appl. Phys. Lett. 93 (2008) 232901. [12] K. Oga, I. Yamada, M. Azuma, S. Takeshita, K.H. Satoh, A. Koda, R. Kadono, M. Takano, Y. Shimakawa, Inorg. Chem. 47 (2008) 7355. [13] A. Kumar, L.W. Martin, S. Denev, J.B. Kortright, Y. Suzuki, R. Ramesh, V. Gopalan, Phys. Rev. B 75 (2007) 060101. [14] A.A. Belik, S. Iikubo, K. Kodama, N. Igawa, S. Shamoto, S. Niitaka, M. Azuma, Y. Shimakawa, M. Takano, F. Izumi, E. Takayama-Muromachi, Chem. Mater. 18 (2006) 798. [15] T. Katsumata, A. Takase, M. Yoshida, Y. Inaguma, J.E. Greedan, J. Barbier, L.M.D. Cranswick, M. Bieringer, Mater. Res. Soc. Symp. Proc. 988 (2007) QQ06-03. [16] A.C. Larson, R.B. Von Dreele, General Structure Analysis System (GSAS), Los Alamos National Laboratory Report LAUR 86-748, 2004. [17] D. Lebeugle, D. Colson, A. Forget, M. Viret, A.M. Bataille, A. Gukasov, Phys. Rev. Lett. 100 (2008) 227602. [18] T.P. Comyn, T. Stevenson, M. Al-Jawad, S.L. Turner, R.I. Smith, A.J. Bell, R. Cywinski, J. Appl. Phys. 105 (2009) 094108. [19] T. Stevenson, T.P. Comyn, A. Daoud-Aladine, A.J. Bell, J. Magn. Magn. Mater. 322 (22) (2010) L64.
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Letter to the Editor
Antiferromagnetic order in tetragonal bismuth ferrite–lead titanate Tim P. Comyn a,n, Tim Stevenson a, Maisoon Al-Jawad b, Gilles Andre´ c, Andrew J. Bell a, Robert Cywinski d a
Institute for Materials Research, University of Leeds, Leeds LS2 9JT, UK Centre for Oral Growth and Development, Dental Physical Sciences Group, Queen Mary, University of London, London E1 4NS, UK Laboratoire Le´on Brillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France d School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH, UK b c
a r t i c l e i n f o
abstract
Article history: Received 3 December 2010 Received in revised form 10 March 2011 Available online 13 June 2011
Neutron powder diffraction of particulates of 0.7BiFeO3–0.3PbTiO3 in the tetragonal P4mm phase has been used to determine the type of antiferromagnetic order that occurs below 220 K. It is shown that G-type antiferromagnetic ordering occurs, with magnetic propagation along the 12 12 12 direction. Unlike the rhombohedral R3c phase the direction of antiferromagnetic propagation and the ferroelectric order parameter are not parallel in the tetragonal phase, but at an angle of 49.91. The ground state (at 4 K) magnetic moment is 4.1 mB. & 2011 Elsevier B.V. All rights reserved.
Keywords: Bismuth ferrite Multiferroic Neutron diffraction Antiferromagnetic Ferroelectric Tetragonal
1. Introduction Bismuth ferrite, BiFeO3, is one of the few known roomtemperature multiferroics, displaying both G-type antiferromagnetic and ferroelectric order [1]. It readily forms a solid solution with ferroelectric PbTiO3, resulting in the system xBiFeO3 (1x)PbTiO3, which is also multiferroic at room temperature [2–8] for a wide range of x. Single phase perovskite is more easily achievable in the solid solution than in BiFeO3 [9], whilst DC resistivity values and electric-field induced strains are of the same order as one would expect for undoped lead zirconate titanate (PZT) [10]. We have shown previously that for 0.7BiFeO3–0.3PbTiO3, which is close to the R3c–P4mm phase boundary, the crystallographic phase content is form dependent [11]. Particulate material has a predominantly tetragonal perovskite structure (P4mm) and is paramagnetic at room temperature, as determined using neutron diffraction, whereas dense ceramics are predominantly rhombohedral and display antiferromagnetic order under ambient conditions. Zhu et al. [6] have confirmed the existence of antiferromagnetic order for tetragonal compositions in the range 0.45ox o0.69 using zero-field cooling with SQUID (superconducting quantum interference device) measurements at sub-ambient temperatures. For the composition x¼0.69, a Ne´el temperature of 220 K was recorded.
The identity and magnetic structure of this low temperature tetragonal perovskite antiferromagnetic phase are unknown. There are a number of reported primitive tetragonal perovskites in which magnetic ordering occurs: PbVO3 (P4mm) shows two-dimensional antiferromagnetic order below 43 K [12], plus the observation of either spin-glass or G-type antiferromagnetic order in thin film form [13]; BiCoO3 (P4mm) is a C-type antiferromagnetic with a Ne´el temperature of 470 K [14]; 0.5PbFeO2F–0.5PbTiO3 (P4mm) shows G-type antiferromagnetic order with a Ne´el temperature of 450 K, and a propagation vector k ¼ 12 12 12 [15]. Although 0.5PbFeO2F–0.5PbTiO3 displays the same space group as tetragonal 0.7BiFeO3–0.3PbTiO3, the spontaneous strain or tetragonality (c a)/a is very different. At room temperature and at 4 K, the spontaneous strain of 0.5PbFeO2F–0.5PbTiO3 is extremely low, ca. 0.2%—splitting of the 001/100 peaks in the diffraction data is not evident; 0.7BiFeO3–0.3PbTiO3, however, shows a colossal spontaneous strain of ca. 19% [4], two orders of magnitude larger. The objective of the work reported here was to solve the structure of the antiferromagnetic tetragonal phase of 0.7BiFeO3– 0.3PbTiO3 as a function of temperature, and determine the magnetic ground state. Differences in magnetic structure will be sought with the rhombohedral BiFeO3 end member.
2. Experimental n
Corresponding author. Tel.: þ44 113 3432540; fax: þ44 113 3432384. E-mail address: [email protected] (T.P. Comyn).
0304-8853/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2011.06.009
The powders were formed by rapidly cooling dense ceramic bodies, leading to disintegration as reported previously, generating
2534
T.P. Comyn et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 2533–2535
a predominantly tetragonal material [11]. Neutron diffraction data were gathered using G4.1, a reactor neutron facility at Laboratoire Le´on Brillouin (LLB), France. The powder samples were loaded into vanadium cans, and measurements were taken at room temperature, at 4 K, then upon continuous heating back to room temperature; each temperature point presented is the average of a temperature range of ca. 20 K. Typical collection times were of the order of 40 min per temperature point. A wavelength of 2.4226 A˚ was used. Rietveld refinements were performed using GSAS [16] in order to validate the proposed structural and magnetic models. The magnetic structure was separated from the nuclear lattice in order to alleviate the constraints imposed by the P4mm symmetry. The lattice constants of the magnetic model, containing only magnetic contributions from Fe3 þ with an occupancy of x¼0.7 (akin to 0.7BiFeO3–0.3PbTiO3), were constrained to that of the nuclear structure. The room temperature structural model previously reported was used as a precursor.
Fig. 2. Structural and magnetic refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K; the zoomed region clearly shows the magnetic peaks, which are absent at room temperature.
3. Results and discussion Fig. 1 and Table 1 show the data collected at 4 K, along with refinement and residual. In order to generate a satisfactory fit, it was necessary to generate a large magnetic super-cell containing eight Fe3 þ ions with an occupancy of 0.7 per site, akin to the nuclear phase, with lattice constants a and c double that of the nuclear tetragonal model. Fig. 2 shows an enlarged region of Fig. 1 displaying magnetic Bragg peaks at 30.41 and 54.91, which are absent in data collected at room temperature. These peaks are assigned the labels 12 12 12M and 12 12 32M, respectively. In constructing the magnetic model a number of different scenarios for the spin directions were trialed in order to determine the magnetic moment vector, but due to the dominance of the nuclear model similar refinement residuals were obtained in
Fig. 3. Structure of 0.7BiFeO3–PbTiO3. Only Bi (white), Fe (blue, with arrows), and O (red) are shown. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 1. Structural and magnetic refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K.
Table 1 Results of structural and magnetic Rietveld refinement for 0.7BiFeO3–0.3PbTiO3 powder collected at 4 K. Composition
0.7BiFeO3–0.3PbTiO3, 4 K
Phase Weight fraction Moment per Fe3 þ (mB) ˚ Lattice parameters (A)
R3c 0.09(2) 0 a¼ 5.57(1) c ¼13.8(5) Rp ¼7.2, Rwp ¼ 5.2
Residuals (%)
P4mm 0.90(8) 4.1(0) a¼3.805(5) c¼ 4.525(1)
each case. The model generated, with the moments parallel to the propagation vector k ¼ 12 12 12 is shown in Fig. 3. An excellent fit is achieved between the data and the model employing G-type antiferromagnetic order along the 111 direction for the P4mm phase, suggesting a similar structure to 0.5PbFeO2F–0.5PbTiO3, ˚ c¼3.982, (ca)/ which has a low tetragonal distortion (a¼3.974 A, a¼0.2%, and moment per Fe3 þ ¼3.5 mB at 4 K) and magnetic propagation vector k ¼ 12 12 12 . Clearly the tetragonal distortion in this system is far higher, (c a)/a¼18.9% at 4 K. The nuclear and magnetic model generated shows that, unlike in the R3c phase, the antiferromagnetic propagation direction is not aligned with the ferroelectric order parameter but, as depicted in Fig. 4, differs by 49.91. This is contrary to that observed in rhombohedral BiFeO3 [17] and 0.9BiFeO3–0.1PbTiO3 [18], where the polar direction lies in the plane of the magnetic cycloid. It is assumed that the same is also true for other BiFeO3based R3c materials such as 0.7BiFeO3–0.3PbTiO3 prepared in dense ceramic form. However, with the present analysis, it was not possible to determine the absolute direction of magnetic moments, to clarify whether they are parallel to the ferroelectric order parameter (0 0 1) or not.
T.P. Comyn et al. / Journal of Magnetism and Magnetic Materials 323 (2011) 2533–2535
Fig. 4. Primitive unit cell for 0.7BiFeO3–0.3PbTiO3. In the rhombohedral phase (R3c) the antiferromagnetic and ferroelectric ordering directions are aligned, whereas in the tetragonal phase (P4mm) they are not.
2535
Using a combination of P4mm and R3c nuclear phases, and the model constructed at 4 K as a starting point, refinements were performed as a function of temperature. The concentration of the R3c phase was found to be 10.571.5 wt%, and was independent of temperature, providing an indication of a temperature independent phase boundary. The refined moment as a function of temperature is shown in Fig. 6. The Ne´el temperature as reported by Zhu et al. for the similar composition 0.69BiFeO3–0.31PbTiO3 is marked in the figure as a dashed vertical line (220 K); the data presented here suggests a Ne´el temperature in good agreement with this. Above 220 K non-zero values are obtained from the refinement, suggesting considerable short range order; the errors from the refinement are also large at this point.
4. Conclusions The tetragonal phase that exists in 0.7BiFeO3–0.3PbTiO3 displays G-type antiferromagnetic ordering below ca. 220 K. At 4 K, the magnetic moment is 4.1 mB. Contrary to observations in the rhombohedral R3c phase in BiFeO3 and 0.9BiFeO3–0.1PbTiO3, the ferroelectric order parameter and direction of antiferromagnetic propagation in the tetragonal phase are misaligned by 49.91. The structure is similar to that reported for the composition 0.5PbFeO2F–0.5PbTiO3.
Acknowledgments
Fig. 5. Neutron powder diffraction data collected on G4.1 (LLB) and HRPD (ISIS). The inset shows the 32 12 12 peak, visible using HRPD. The model generated here fits well with this data.
The authors gratefully acknowledge Aziz Daoud-Aladine and the Science and Technology Facilities Council, for the data collected on HRPD. References
Fig. 6. Refined magnetic moment for tetragonal 0.7BiFeO3–0.3PbTiO3 as a function of temperature.
The G-type P4mm refinement predicts the presence of a peak ˚ However, this cannot be observed using the resolution at 2.329 A. of G4.1. Fig. 5 shows a combination of the data collected using G4.1 at LLB at 4 K plus data from HRPD at ISIS at 7.5 K (STFC, Didcot, UK), as reported previously [19]. The 32 12 12 reflection can be clearly seen in the inset; here the data are shown as crosses (a number of crosses are omitted to improve clarity) and the refinement is shown as a solid line. Note that in Fig. 5, d-spacing rather than 2y is used on the abscissa.
[1] P. Fisher, M. Polomska, I. Sosnowska, M. Szyman´ski, J. Phys. C 13 (1980) 1931. [2] R.T. Smith, G.D. Achenbach, R. Gerson, W.J. James, J. Appl. Phys. 39 (1) (1968) 70. [3] S.A. Fedulov, P.B. Ladyzhinskii, I.L. Pyatigorskaya, Y.N. Venevtsev, Sov. Phys.—Solid State 6 (2) (1964) 375. [4] V.V.S.S. Sai Sunder, A. Halliyal, A.M. Umarji, J. Mater. Res. 10 (1995) 1301. [5] D.I. Woodward, I.M. Reaney, R.E. Eitel, C.A. Randall, J. Appl. Phys. 94 (5) (2003) 3313. [6] W.-M. Zhu, H.-Y. Guo, Z.-G. Ye, Phys. Rev. B 78 (2008) 014401. [7] S. Bhattacharjee, D. Pandey, J. Appl. Phys. 107 (2010) 124112. [8] R. Ranjan, K.A. Raju, Phys. Rev. B 82 (2010) 054119. [9] T.P. Comyn, S.P. McBride, A.J. Bell, Mater. Lett. 58 (2004) 3844. [10] T.P. Comyn, T. Stevenson, A.J. Bell, J. Phys. IV 128 (2005) 13. [11] T.P. Comyn, T. Stevenson, M. Al-Jawad, S.L. Turner, R.I. Smith, W.G. Marshall, A.J. Bell, R. Cywinski, Appl. Phys. Lett. 93 (2008) 232901. [12] K. Oga, I. Yamada, M. Azuma, S. Takeshita, K.H. Satoh, A. Koda, R. Kadono, M. Takano, Y. Shimakawa, Inorg. Chem. 47 (2008) 7355. [13] A. Kumar, L.W. Martin, S. Denev, J.B. Kortright, Y. Suzuki, R. Ramesh, V. Gopalan, Phys. Rev. B 75 (2007) 060101. [14] A.A. Belik, S. Iikubo, K. Kodama, N. Igawa, S. Shamoto, S. Niitaka, M. Azuma, Y. Shimakawa, M. Takano, F. Izumi, E. Takayama-Muromachi, Chem. Mater. 18 (2006) 798. [15] T. Katsumata, A. Takase, M. Yoshida, Y. Inaguma, J.E. Greedan, J. Barbier, L.M.D. Cranswick, M. Bieringer, Mater. Res. Soc. Symp. Proc. 988 (2007) QQ06-03. [16] A.C. Larson, R.B. Von Dreele, General Structure Analysis System (GSAS), Los Alamos National Laboratory Report LAUR 86-748, 2004. [17] D. Lebeugle, D. Colson, A. Forget, M. Viret, A.M. Bataille, A. Gukasov, Phys. Rev. Lett. 100 (2008) 227602. [18] T.P. Comyn, T. Stevenson, M. Al-Jawad, S.L. Turner, R.I. Smith, A.J. Bell, R. Cywinski, J. Appl. Phys. 105 (2009) 094108. [19] T. Stevenson, T.P. Comyn, A. Daoud-Aladine, A.J. Bell, J. Magn. Magn. Mater. 322 (22) (2010) L64.