Effects of La-doping on the ferrimagnetism in double perovskite Y2MnCrO6

Accepted Manuscript Effects of La-doping on the ferrimagnetism in double perovskite Y2MnCrO6 Zhongfeng Zhang, Lin Hao, Xiangnan Xie, Haoru Wang, Qingxuan Yu, Hong Zhu PII:

S0925-8388(15)01485-1

DOI:

10.1016/j.jallcom.2015.05.158

Reference:

JALCOM 34280

To appear in:

Journal of Alloys and Compounds

Received Date: 2 March 2015 Revised Date:

15 May 2015

Accepted Date: 16 May 2015

Please cite this article as: Z. Zhang, L. Hao, X. Xie, H. Wang, Q. Yu, H. Zhu, Effects of La-doping on the ferrimagnetism in double perovskite Y2MnCrO6, Journal of Alloys and Compounds (2015), doi: 10.1016/ j.jallcom.2015.05.158. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.

RI PT

ACCEPTED MANUSCRIPT

Effects of La-doping on the ferrimagnetism in double

SC

perovskite Y2MnCrO6

M AN U

Zhongfeng Zhang, Lin Hao, Xiangnan Xie, Haoru Wang, Qingxuan Yu, and Hong Zhu*

Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026,

AC C

EP

TE D

China

* Corresponding author. Hong Zhu Department of Physics University of Science & Technology of China 96 Jinzhai Road Hefei, Anhui, 230026, P.R.China E-mail: [email protected] Tel: +86-551-63600797 FAX: +86-551-63601073

ACCEPTED MANUSCRIPT Abstract The La3+ doped Y2-2yLa2yMnCrO6 (y = 0–0.4, 0.9) polycrystalline samples have been synthesized by means of a standard solid-state reaction method. For lightly

RI PT

doped samples with y ≤ 0.3, the refined structural parameters of XRD patterns display a decrease tendency of structural anisotropy with increasing La content, suggesting a gradual reduction of the octahedral tilting in the compounds with increasing A-site

SC

cation size. The temperature dependence of magnetization gives that the ferrimagnetic

M AN U

state at temperatures below ~ 75 K for the prototype Y2MnCrO6 remains till y = 0.3, while the samples with y = 0.4 and 0.9 show a much higher transition temperature at ~ 120 K. However, for the ferrimagnetic samples with y ≤ 0.2，a detailed analysis on the high-temperature paramagnetic susceptibility reveals that the antiferromagnetic

TE D

coupling within the Cr3+ sublattice is obviously enhanced with increasing La3+ content, which is an unfavourable factor for the ferrimagnetism. The electrical transport properties of the samples are dominated by the thermal activation mechanism, and the

EP

activation energy decreases distinctly with increasing y (y ≤ 0.3). The results indicate

AC C

that the ferrimagnetism in Y2MnCrO6 oxide is suppressed with increasing A-site average cation size.

Keywords

A-site cation size Cr-doped manganites Ferrimagnetism

ACCEPTED MANUSCRIPT 1. Introduction Transition metal oxides, usually with a perovskite structure ABO3, have attracted a great deal of attention over the past decades, largely because of their unique

RI PT

physical properties such as superconductivity [1], colossal magnetoresistance [2, 3], metal-insulator transition [4], ferroelectricity [5] and multiferroicity properties [6, 7].

SC

From an application point of view, the related functionalities open up new frontiers in various devices, for example, multiferroic YMnO3 presents opportunities for

M AN U

potential applications in multi-state memories, the emerging field of spintronics, new types of attenuators, sensors, and so on. With an antiferromagnetic ground-state, however, YMnO3 is insensitive to external magnetic field, which is a negative factor for its functionality. Therefore, it is imperative to enhance

TE D

ferromagnetic component in related perovskite oxides.

It is well known that structural, electrical, and magnetic properties of these

EP

oxides, in which the BO6 octahedra with corner-shared oxygen ions form a three dimensional network and the larger A-site cations sit in the 12-coordinate

AC C

cubo-octahedral cavities, are very sensitive to stoichiometry and chemical substitutions onto all the three sites. As an example, the prototype compound LaMnO3 undergoes a transition from A-type antiferromagnetic insulator, through ferromagnetic metal, to G-type antiferromagnetic insulator with increasing divalent element (such as Ca, Sr and Ba) substitution on the La-site, accompanying with a structural transition from orthorhombic to cubic symmetry.

ACCEPTED MANUSCRIPT Besides these, recently it has been gradually understood that cation ordering, which can occur on either A- or B-site, is also an effective tailoring method for perovskite oxides. Among them, most studies have been focused on B-site ordered

RI PT

oxides named double perovskite A2B'B''O6, with a similar structure to the simple perovskite except that the B' and B'' cations are arranged alternately in an ordered manner. For instance, Sr2FeMoO6 with B-site ordering shows a colossal

SC

magnetoresistance (CMR)-type half-metallic ferromagnetism [8], with a significantly

M AN U

high room temperature MR ratio depending on the ordering degree of B-site cations. La2MMnO6 (M = Co, Ni) shows a high Curie temperature [9, 10], which has also been predicted upon the 180° ferromagnetic superexchange interaction in the Goodenough-Kanamori rules [11-13].

TE D

In our previous work, we reported ferrimagnetism instead of antiferromagnetism in half-doped YMn0.5Cr0.5O3, suggesting the occurrence of B-site cation ordering in the compound [14]. Recently, by means of Retvield refinement to the X-ray

EP

diffraction patterns and first-principles calculations, our study revealed that (001)

AC C

layered B-site cation ordering is rational for the half-Cr doped YMnO3 compound [15], which is described as the formula Y2MnCrO6 (YMCO) hereafter. Fig. 1 shows the structure schematic drawing of Mn/Cr (001) layer ordered Y2MnCrO6, which has a monoclinic structure of the P21/b space group with a = 5.2497(0) Å, b = 5.6401(1) Å, c = 7.4679(1) Å and α = 89.97(8)°. For comparing with pseudo-cubic structure of doped mangnites, we transform it into a triclinic structure with as = bs =

a 2 + b 2 =7.7054 Å, cs = c = 7.4679 Å and in-plane included angle θ = 94.108°,

ACCEPTED MANUSCRIPT which corresponds to a superstructure of 2ac × 2ac × 2ac (ac is a lattice parameter for a cubic perovskite). It is noteworthy that the cs axis, along which the MnO6 and CrO6 octahedral layers alternately stack, is considerably shorter than the in-plane axes as/bs.

RI PT

On the other hand, as well known, the B-site cation ordering in double perovskites A2B'B''O6 usually occurs in the case of large charge or size difference between B' and B'' cations [16]. Whereas in the present case, Mn3+ (3d4) and Cr3+ (3d3) are two ions

SC

with similar radii, so the B-site cation ordering in YMCO still appears to some

M AN U

unnatural. Now we are considering appropriate octahedral tilting distortion due to small Y3+ cation on the A-site and Jahn-Teller distortions resulted from Mn3+ ion as the possible reasons.

To investigate this issue in detail, we choose larger La3+ ion (1.36 Å) to

TE D

substitute for Y3+ (1.075 Å) on the A-site. By increasing A-site cation size, the tilting distortion of Mn/CrO6 octahedral should be partially relieved. In this paper we report the synthesis and characterization of Y2-2yLa2yMnCrO6 (y = 0–0.4, 0.9) compounds

EP

with particular focus on the effects of A-site average cation size on the ferrimagnetism.

AC C

The main conclusions of our study are (i) the substitution of larger La3+ ions gradually reduces the structural anisotropy of the compounds, (ii) the antiferromagnetic exchange interaction within Cr3+ sublattice increases obviously with increasing La3+ content, while ferromagnetic coupling within Mn3+ sublattice and antiferromagnetic coupling between the two sublattices change little. From the opposite angle, these results demonstrate that small Y3+ ion as the A-site cation plays an important role on the ferrimagnetism in YMCO compound.

ACCEPTED MANUSCRIPT 2. Experimental details Polycrystalline Y2-2yLa2yMnCrO6 (0 ≤ y ≤ 0.9) samples were synthesized using La2O3 (99.99%), Y2O3 (99.99%), Cr2O3 (99.9%), and MnO2 as the starting materials

RI PT

by a standard solid-state reaction method. Before weighing, La2O3 and Y2O3 were dehydrated in air at 800˚C for 10 h. Stoichiometric quantities of these oxides were

SC

thoroughly mixed and grinded in an agate mortar, then the mixture was first fired in air at 900˚C for 12 h. The mixture so obtained was ground again and heated at 1200˚C

M AN U

for another 12 h. In the final step, the resultant Y2-2yLa2yMnCrO6 powder was pressed into pellets and sintered at 1400˚C in air for 30 h. Room temperature powder X-ray diffraction (XRD) data were measured with a Rigaku TTRAX-III diffractometer employing CuKα radiation (1.5406 Å) over the range 20˚ ≤ 2θ ≤ 80˚, with a step size

TE D

of 0.02˚. Magnetization (M) as a function of temperature (M–T curve) or field (M–H curve) was measured with a Quantum Design Physical Properties Measurement

EP

System (PPMS). M–T curves were recorded in the temperature range of 2–300 K under a magnetic field of H = 1 kOe with zero-field-cooled (ZFC) and field-cooled

AC C

(FC) modes, respectively. M–H curves were obtained up to 50 kOe magnetic fields at 2 K. Temperature-dependent electrical resistivity (ρ) of the samples was measured by the standard four-probe method in the temperature range of 20–300 K in a home-made apparatus with a cryostat.

3. Results and discussion

3.1. Structural analysis

ACCEPTED MANUSCRIPT Six representative XRD patterns of the Y2-2yLa2yMnCrO6 series with y varying from 0 to 0.9 are displayed in Fig. 2. For y ≤ 0.3, it can be seen that the samples are single phase as YMCO oxide with a monoclinic structure in the P21/b space group

RI PT

[15]. It is clear that the strongest diffraction peak continuously shifts to lower angle side with increasing y, indicating successful substitution of larger La3+ ion on the A-site. At y = 0.3, overlapping (021)/(200) peak at 2θ ~ 34.1˚ splits into two separate

SC

ones. For the y = 0.4 sample, the strongest peak remains at the same position as that

M AN U

for the y = 0.3 sample and an intensive impurity peak corresponding to the y = 0.9 sample appears at left side of the strongest peak, indicating the upper limit for La substitution in YMCO compound is 30%. For y between 0.4 and 0.8, patterns (not shown here) give that all the samples are two-phase mixture and the fraction of

TE D

YMCO phase decreases with increasing y. Up to y = 0.9, as shown in Fig. 2, the sample transforms to a single orthorhombic phase with a = 5.4840 Å, b = 7.7638 Å and c = 5.5102 Å, which is similar to undoped LaCrO3 and LaMnO3 compounds.

EP

After that, we performed the Rietveld refinement of powder XRD data at room

AC C

temperature using the GSAS software [17] for the single-phase samples with y ≤ 0.3 based upon the monoclinic structure of the P21/b space group. Table 1 shows the refined structural parameters of Y2-2yLa2yMnCrO6 (y ≤ 0.3) samples. With increasing La3+ content y, one can see that the longer b axis shortens while the shorter a and c axes extend. To intuitively compare with a pseudo-cubic perovskite, the refined cell was expanded to a triclinic superstructure corresponding to 2ac × 2ac × 2ac as shown in

ACCEPTED MANUSCRIPT Fig.1 [15, 18]. Approximately, the superstructure can be viewed as a pseudo-tetragonal structure with an in-plane included angle θ around 94˚. Fig. 3 summaries the lattice parameters and θ for the pseudo-tetragonal superstructure. With

RI PT

increasing y to 0.3, it can be seen in Fig. 3 that the cs axis between the MnO6 and CrO6 octahedral layers increases about 1.3%, while the as/bs axis within the MnO6/CrO6 octahedral layers increases only 0.54%, implying less difference between

SC

the shorter cs axis and longer as/bs axis. Meanwhile, the in-plane angle θ decreases

M AN U

from 94.1˚ for y = 0 to 92.9˚ for y = 0.3, corresponding to the basal plane approaching a square. These results demonstrate that larger La3+ ion substitution on the A-site results in degradation of structural anisotropy in the YMCO prototype compound. Such a structural transformation to high symmetry has been commonly investigated in

TE D

perovskite oxides with larger A-site cations due to reduced octahedral tilting of BO6 [19-21]. Considering the possibility of layered B-site cation ordering, it may also suggest a gradually random distribution of Mn/Cr ions. To clarify this point, however,

EP

more evidence provided by advanced characterization techniques, such as neutron

AC C

diffraction measurement, is still needed in future. 3.2. Magnetic properties

Fig.

4(a)

shows

the

temperature

dependences

of

magnetization

for

Y2-2yLa2yMnCrO6 (y ≤ 0.4, 0.9) samples with field-cooled (FC) and zero-field-cooled (ZFC) modes at magnetic field H = 1 kOe. For the lightly La3+-doped samples (y ≤ 0.3), with decreasing temperature it can be seen that the magnetization begins to increases sharply at ~ 75 K, which is similar to the ferrimagnetic transition in the

ACCEPTED MANUSCRIPT undoped YMCO sample we reported before [14]. The significant difference between ZFC and FC curves might be related to the high coercivity behavior for the samples as shown below in Fig. 6. The highly La3+-doped sample with y = 0.9 shows a

RI PT

ferromagnetic-like transition at ~120K, which is consistent with reference [22]. For the intermediately doped sample (y = 0.4), besides a sharp increase at ~ 120 K as the former one, the M-T curve shows a kink at ~ 75 K corresponding to the lightly

M AN U

in the XRD pattern analysis for the y = 0.4 sample.

SC

La3+-doped samples, which is in agreement with the two-phase coexistence revealed

To gain some insight into the magnetic properties of the doped samples, we plot −1 the temperature dependence of the inverse paramagnetic susceptibility ( χ mol ) in Fig. −1 4(b). For the samples with low dopant (y ≤ 0.15), the χ mol −T curve is a hyperbola,

TE D

which is a typical feature for ferrimagnetism; while the y = 0.9 sample shows a straight line as usually observed in ferromagnetic materials. However, the y = 0.3 sample displays some distinctive features, i.e., the value of 1/ χ mol falls in between

EP

the two cases mentioned above and the curve shape appears to be a weighted

AC C

superposition of the ferri- and ferromagnetic phases. It reveals that y = 0.3 sample is two-phase coexisted rather than a single phase as shown by the XRD pattern. According to the molecular field theory of ferrimagnetism, the Curie constants of

Cr/Mn sublattice can be expressed by CCr/Mn = Noµog2 µB2 SCr/Mn (SCr/Mn + 1)/3kB, where No denotes the Avogadro constant, µo is the permeability of free space, g = gs = 2 is the Landé g factor, µB is the Bohr magneton, SCr/Mn is the spin quantum number of Cr3+/Mn3+ ions, and kB is the Boltzmann constant, respectively. For those

ACCEPTED MANUSCRIPT single-phase samples with y ≤ 0.20, we fit the inverse magnetic susceptibility data of paramagnetic state at higher temperatures (above 75 K) according to the ferrimagnetic Curie-Weiss law in the form of [23] H T 1 ρ = + − M tot Cmol χ o T − θ

(1)

RI PT

χ mol

=

with Cmol = CCr + CMn

θ= 1

χo

λ 2CCr CMn (1 + a ) CCr − (1 + b ) CMn 

( CCr + CMn )

3

λCCr CMn ( 2 + a + b ) CCr + CMn =

2 λ ( 2CCr CMn − aCCr2 − bCMn )

( CCr + CMn )

2

2

M AN U

ρ=

(2)

SC

1

(3)

(4)

(5)

TE D

where Cmol is the Curie constant, -λ (λ > 0) is the antiferromagnetic molecular field coefficient between the Cr3+- and Mn3+ sublattices, and a and b are the intra-site coefficients normalized by λ. In our previous work the fitting value and theoretical

EP

value of the Curie constant Cmol inosculated very well [14], so here we remain it

AC C

unchanged as the theoretical value of 6.12×10-5 K·m3/mol and optimize other three parameters χ o , ρ and θ. As shown in Fig. 4(b), the fitting curve for the representative y = 0.15 sample is in good agreement with the experimental data. And the fitting parameters for lightly La3+-doped samples are listed in Table 2. Then by solving Equations (3)–(5), we obtained λ , a and b as shown in Fig. 5. It can be seen that the positive values of λ and b correspond to the antiferromagnetic exchange interaction between Mn3+- and Cr3+ sublattices and ferromagnetic

ACCEPTED MANUSCRIPT interaction within Mn3+ sublattice, respectively, which is in favor of ferrimagnetic order in the compounds. Whereas in Cr3+ sublattice, the negative value of a, corresponding to an antiferromagnetic interaction, is a negative factor to

RI PT

ferrimagntism. Considering the absolute value of a is small, the negative intra-site interaction in Cr3+sublattice is suppressed due to the former two interactions, eventually giving rise to a ferrimagnetic state in the compound. With increasing La3+

SC

doping level y, one can see that λ and b change little, indicating the antiferromagnetic

M AN U

interaction between the two sublattices and ferromagnetic interaction within Mn3+ sublattice remain unchanged. However, the absolute value of negative a increases remarkably with increasing y, implying enhancement of the antiferromagnetic interaction within Cr3+ sublattice. In this respect, the ferrimagntism in YMCO

TE D

compound is disrupted in some extent due to larger La3+ substitution on the A-site. Fig. 6 shows the representative M (H) curve of the Y2-2yLa2yMnCrO6 compounds at 2 K. For the ferromagnetic y = 0.9 sample, it shows a negligible coercive field and

EP

a saturation magnetization (Ms) of 2.5 µB/f.u., which is much less than the theoretical

AC C

value 7 µB/f.u. calculated from high-spin Mn3+ and Cr3+ ions. The difference might be due to the variation in valence state and spin configuration of the two cations and the details will be investigated in further work. As for the ferrimagnetic samples with y ≤ 0.2, the saturation magnetizations are around 1 µB/f.u., corresponding to antiparallel arrangement of high-spin Mn3+ (3d4/4µB) and Cr3+ (3d3/3µB). The considerable large coercive field (Hc ~ 106 A/m) for these ferrimagnetic samples can be attributed to uniaxial anisotropy of the pseudo-tetragonal structure. One can see that the coercive

ACCEPTED MANUSCRIPT field decreases obviously with increasing La3+ ion substitution on the A-site, which is consistent with the reduction of structural anisotropy as discussed above. 3.3. Resistivity

RI PT

The electrical resistivity measurements as a function of temperature are plotted in the inset of Fig. 7 for Y2-2yLa2yMnCrO6 (y ≤ 0.3) samples. All the samples show a

SC

typical insulator behavior in the temperature range 200–300 K. With decreasing temperature, the resistivity increases rapidly. The electrical resistivity data in the

M AN U

paramagnetic phase of doped manganites have been usually fitted by the thermal activation model, which follows the well-known Arrhenius relation:

ρ = ρ0 exp( Ea / kBT )

(6)

temperature.

TE D

where kB is the Boltzmann constant, Ea is activation energy and T is absolute

In order to investigate in detail the effect of La-doping on the electrical transport

EP

behavior, we replotted the resistivity curves as ln(ρ) vs. 1000/T, and fitted resistivity data using the Arrhenius relation. Fig. 7 shows the experimental data (scatter symbols)

AC C

and fitting results (solid lines). It can be seen that the fitting results are in good agreement with the data for the whole temperature range of measurement. The most important fitting parameter, i.e. activation energy Ea for Y2-2yLa2yMnCrO6 (y ≤ 0.3) samples are listed in Fig. 8. It is clear that the activation energy decreases gradually from Ea = 0.31 eV to 0.27 eV with increasing La3+ substitution from y = 0.0 to 0.3, indicating that A-site cation size strongly affects the hopping probability of eg electrons. As well known, delocalization of eg electrons in manganites is governed by

ACCEPTED MANUSCRIPT the overlap of Mn/Cr 3d orbitals and O 2p orbitals. Accordingly, with increasing the A-site cation size by La3+ substation in the YMCO series, decreased octahedral tilting, which corresponds to high symmetry structure transformation, leads to an increase in

RI PT

the magnitude of the 3d-2p orbital overlap. As a result, improvement of the hopping probability of eg electrons corresponds to the smaller activation energy Ea for larger La3+ substitution on the A-site.

SC

As discussed above, degradation of the structural anisotropy in YMCO by larger

M AN U

La3+ ion substitution on the A site implies a reduction in octahedral tilting of Mn/CrO6 as normally observed in manganites. Because the radius of 6-coordinate Cr3+ ion (0.615 Å) is smaller than that of Mn3+ (0.645 Å) in octahedron geometry, we consider that the octahedral tilting of CrO6 relaxes more likely than MnO6 octahedra.

TE D

Consequently, the antiferromagnetic exchange interaction within the Cr sublattice improves obviously with increasing average ion size on the A-site, while the other two exchange interactions change little. Another possible reason might be related to the

EP

anti-site disorder in B-site cation ordered perovskite oxides. At the moment, however,

AC C

we cannot validate this point due to the limitation of XRD on distinguishing between Cr and Mn elements. To clarify the B-site cation ordering in YMCO compound, further investigations by means of neutron diffraction technique will be need.

4. Conclusions

In this paper, we have synthesized La-doped Y2-2yLa2yMnCrO6 (y = 0.0–0.4, 0.9) polycrystalline samples successfully and preliminarily investigated the evolution of

ACCEPTED MANUSCRIPT structure, magnetic, and transport properties during La3+ ion substitution on the A-site. Powder XRD patterns demonstrate that the lightly La3+ doped samples (y ≤ 0.3) have a single phase of pseudo-tetragonal structure similar to prototype Y2MnCrO6

RI PT

compound. With increasing doping level y to 0.3, the structural anisotropy gradually diminishes, i.e., the difference between the in-plane and out-of-plane axes becomes smaller. While the temperature dependence of magnetic susceptibility gives that the

SC

low-temperature ferrimagnetic state remains for the lightly La3+ doped samples, a

M AN U

detailed analysis on the paramagnetic Curie-Weiss behaviour at high temperatures reveals that the antiferromagnetic interaction within the Cr3+ sublattice is considerably enhanced with increasing La3+ substitution. The electrical transport properties of the samples are dominated by the thermal activation mechanism, and the activation

TE D

energy decreases obviously with increasing y (y ≤ 0.3). As a result, larger La3+ ion substitution on the A-site shows an adverse tendency to the ferrimagnetism in Y2-2yLa2yMnCrO6 compounds.

EP

Acknowledgements

AC C

We would like to thank Dr. Li Pi for valuable discussions and technical help during the experiment. This work is supported by the National Natural Science Foundation of China (Grant No. 11174261 and 11474262). References [1] P. Monthoux, D. Pines, G.G. Lonzarich, Superconductivity without phonons, Nature 450 (2007) 1177-1183. [2] R. Von helmolt, J. Wecker, B. Holzapfel, L. Schultz, K. Samwer, Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films, Phys. Rev. Lett. 71 (1993) 2331-2333. [3] S. Jin, T.H. Tiefel, M. Mccormack, R.A. Fastnacht, R. Ramesh, L.H. Chen, Thousandfold

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

change in resistivity in magnetoresistive La-Ca-Mn-O films, Science 264 (1994) 413-415. [4] M. Imada, A. Fujimori, Y. Tokura, Metal-insulator transitions, Rev. Mod. Phys. 70 (1998) 1039-1263. [5] R.E. Cohen, Origin of ferroelectricity in perovskite oxides, Nature 358 (1992) 136-138. [6] T. Kimura, T. Goto, H. Shintani, K. Ishizaka, T. Arima, Y. Tokura, Magnetic control of ferroelectric polarization, Nature 426 (2003) 55-58. [7] J. Wang, J.B. Neaton, H. Zheng, V. Nagarajan, S.B. Ogale, B. Liu, D. Viehland, V. Vaithyanathan, D.G. Schlom, U.V. Waghmare, N.A. Spaldin, K.M. Rabe, M. Wuttig, R. Ramesh, Epitaxial BiFeO3 Multiferroic Thin Film Heterostructures, Science 299 (2003) 1719-1722. [8] K.-I. Kobayashi, T. Kimura, H. Sawada, K. Terakura, Y. Tokura, Room-temperature magnetoresistance in an oxide material with an ordered double-perovskite structure, Nature 395 (1998) 677-680. [9] G. Blasse, Ferromagnetic interactions in non-metallic perovskites, J. Phys. Chem. Solids 26 (1965) 1969-1971. [10] G.H. Jonker, Magnetic and semiconducting properties of perovskites containing manganese and cobalt, J. Appl. Phys. 37 (1966) 1424-&. [11] J. Goodenough, A. Wold, R.J. Arnott, N. Menyuk, Relationship between crystal symmetry and magnetic properties of ionic compounds containing Mn3+, Phys. Rev. 124 (1961) 373-&. [12] J.B. Goodenough, Theory of the role of covalence in the perovskite-type manganites [La,M(II)]MnO3, Phys. Rev. 100 (1955) 564-573. [13] J. Kanamori, Superexchange interaction and symmetry properties of electron orbitals, J. Phys. Chem. Solids 10 (1959) 87-98. [14] L. Yang, Q. Duanmu, L. Hao, Z. Zhang, X. Wang, Y. Wei, H. Zhu, Ferrimagnetism and possible double perovskite structure in half Cr-doped YMn0.5Cr0.5O3, J. Alloys Comp. 570 (2013) 41-45. [15] L. Hao, L. Yang, M.-H. Lee, T.-H. Lin, Z. Zhang, X. Xie, H. Zhu, Layered B-site cation ordering: A key factor in ferrimagnetism of Y2MnCrO6, J. Alloys Comp. 601 (2014) 14-18. [16] G. King, P.M. Woodward, Cation ordering in perovskites, J. Mater. Chem. 20 (2010) 5785-5796. [17] A.C.Larson, R.B.V. Dreele, General Structure Analysis System (GSAS), Los Alamos Natl. Lab. Rep. (2004) 86-748. [18] M.T. Anderson, K.R. Poeppelmeier, La2CuSnO6: a new perovskite-related compound with an unusual arrangement of B cations, Chem. Mater. 3 (1991) 476-482. [19] P.M. Woodward, T. Vogt, D.E. Cox, A. Arulraj, C.N.R. Rao, P. Karen, A.K. Cheetham, Influence of cation size on the structural features of Lu1/2A1/2MnO3 perovskites at room temperature, Chem. Mater. 10 (1998) 3652-3665. [20] H. Mizoguchi, H.W. Eng, P.M. Woodward, Probing the electronic structures of ternary perovskite and pyrochlore oxides containing Sn4+ or Sb5+, Inorg. Chem. 43 (2004) 1667-1680. [21] A. Vailionis, H. Boschker, W. Siemons, E.P. Houwman, D.H.A. Blank, G. Rijnders, G. Koster, Misfit strain accommodation in epitaxial ABO3 perovskites: Lattice rotations and lattice modulations, Phys. Rev. B 83 (2011) 064101. [22] P. Barrozo, J. Albino Aguiar, Ferromagnetism in Mn half-doped LaCrO3 perovskite, J. Appl. Phys. 113 (2013) 17E309. [23] B.D. Cullity, C.D.Graham, Introduction to Magnetic Materials, in: John Wiley & Sons,

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

Ferrimagnetism, Inc., Hoboken, New Jersey, 2009, pp, 183-190.

ACCEPTED MANUSCRIPT Tables a (Å)

b (Å)

c (Å)

α (˚)

y = 0.00

5.242

5.627

7.457

89.75

y = 0.05

5.253

5.629

7.471

89.79

y = 0.10

5.262

5.621

7.479

89.85

y = 0.15

5.289

5.627

7.515

89.89

y = 0.20

5.291

5.613

7.523

89.86

y = 0.25

5.30

5.609

7.54

89.82

y = 0.30

5.329

M AN U

SC

RI PT

Sample

5.602

7.558

89.72

Table 1. Refined structural parameters of Y2-2yLa2yMnCrO6 (y ≤ 0.3) samples at room

Sample

χo (m3/mol)

ρ (K·mol/m3)

θ (K)

1.12×10-6

8.03×106

67.32

EP

y = 0.00

TE D

temperature.

8.40×10-7

1.55×107

62.80

y = 0.10

9.94×10-7

1.98×107

56.65

y = 0.15

6.58×10-7

4.74×107

45.33

y = 0.20

7.68×10-7

7.25×108

21.19

AC C

y = 0.05

Table 2. The fitting parameters χo、ρ and θ for Y2-2yLa2yMnCrO6 (y ≤ 0.2) samples, which are obtained by fitting the inverse susceptibility to χ-1 = T/Cmol + χo-1 - ρ/(T θ).

ACCEPTED MANUSCRIPT Figure captions Fig. 1. The structure schematic drawing of Mn/Cr (0 0 1) layer ordered Y2MnCrO6, where the Mn/Cr ions are represented by the yellow and green spheres, respectively, while the Y cations and O ions have been omitted for clarity. The superstructure

RI PT

corresponds to 2ac × 2ac × 2ac (ac is a lattice parameter for a cubic perovskite) is indicated by the black dotted lines.

Fig. 2. X-ray powder-diffraction patterns for Y2-2yLa2yMnCrO6 (y = 0, 0.2, 0.3, 0.4,

bs (Å),

cs (Å), and θ (˚) with y for

M AN U

Fig. 3. Variations of lattice parameters as (Å),

SC

0.9) at room temperature.

Y2-2yLa2yMnCrO6 after the Rietveld refinement，in which θ is angle between the asand bs- in a-b plane.

Fig. 4. (a) Temperature dependence of the field-cooled (FC) and zero- field-cooled

TE D

(ZFC) dc molar magnetization of Y2-2yLa2yMnCrO6 (y = 0.05, 0.15, 0.3, 0.4, 0.9) measured at magnetic field of 1 kOe. (b) Representative temperature dependence of the inverse molar magnetic susceptibility (data points) for the samples with y = 0.15, 0.3 and 0.9 and the Curie-Weiss fitting of the paramagnetic behavior (solid line) for

EP

the ferromagnetic samples with y = 0.15.

AC C

Fig. 5. Molecular field coefficient λ between the nearest-neighbor ions, and normalized local molecular field coefficients of the next-nearest ions a/b in Cr3+/Mn3+ sublattice, which are obtained by fitting the inverse magnetic susceptibility data of high-temperature paramagnetic phase according to the Curie-Weiss law for Y2-2yLa2yMnCrO6 ( y ≤ 0.2). Fig. 6. Magnetic moment per formula unit as a function of applied magnetic field for Y2-2yLa2yMnCrO6 (y = 0.1, 0.2, 0.3, 0.9) at 2 K. Fig. 7. The fitting results of the thermal activated model for the experimental

ACCEPTED MANUSCRIPT resistivity data of Y2-2yLa2yMnCrO6 (y = 0.05, 0.15, 0.2, 0.3). The solid lines show the best-fitting curves by using the Arrhenius equation. The inset shows corresponding temperature dependence of the electrical resistivity. Fig. 8. Activation energy Ea obtained by fitting the experimental resistivity data based

AC C

EP

TE D

M AN U

SC

RI PT

upon the thermal activation model for Y2-2yLa2yMnCrO6 (y ≤ 0.3) compounds.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT Substitution of larger La3+ ion results in a reduction of the octahedral tilting in Y2MnCrO6. Antiferromagnetic coupling within the Cr3+ sublattice is obviously enhanced with

RI PT

increasing La3+. The small Y3+ ion plays an crucial role on the ferrimagnetism in the parent

AC C

EP

TE D

M AN U

SC

compound.

ACCEPTED MANUSCRIPT

Prime Novelty Statement In this work we report the synthesis and characterization of Y2-2yLa2yMnCrO6 (y = 0–0.4, 0.9) compounds with particular focus on the effects of A-site average cation

RI PT

size on the ferrimagnetism. The main results of our study are: (i) substitution of larger La3+ ion gradually reduces the structural anisotropy of the compounds; (ii) the antiferromagnetic component within Cr3+ sublattice increases obviously with

SC

increasing La3+ content. The results indicate that the ferrimagnetism in Y2MnCrO6

AC C

EP

TE D

M AN U

oxide is suppressed with increasing A-site average cation size.