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Lattice-distortion Induced Magnetic Transition from Low-temperature Antiferromagnetism to High-temperature Ferrimagnetism in Double Perovskites A2FeOsO6 (A = Ca, Sr).

Hou YS, Xiang HJ, Gong XG - Sci Rep (2015)

Bottom Line: High-temperature insulating ferrimagnetism is investigated in order to further reveal its physical mechanisms, as well as identify potentially important scientific and practical applications relative to spintronics.Also discussed is the 5d(3)-3d(5) superexchange.We propose that such superexchange is intrinsically antiferromagnetic instead of ferromagnetic as previously thought.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China.

ABSTRACT
High-temperature insulating ferrimagnetism is investigated in order to further reveal its physical mechanisms, as well as identify potentially important scientific and practical applications relative to spintronics. For example, double perovskites such as Sr2FeOsO6 and Ca2FeOsO6 are shown to have puzzling magnetic properties. The former is a low-temperature antiferromagnet while the latter is a high-temperature insulating ferrimagnet. In order to understand the underlying mechanisms, we have investigated the frustrated magnetism of A2FeOsO6 by employing density functional theory and maximally-localized Wannier functions. We find lattice distortion enhances the antiferromagnetic nearest-neighboring Fe-O-Os interaction, however weakens the antiferromagnetic interactions via the Os-O-O-Os and Fe-O-Os-O-Fe paths, so is therefore responsible for the magnetic transition from the low-temperature antiferromagnetism to the high-temperature ferrimagnetism as the decrease of the A(2+) ion radii. Also discussed is the 5d(3)-3d(5) superexchange. We propose that such superexchange is intrinsically antiferromagnetic instead of ferromagnetic as previously thought. Our work clearly illustrates the magnetic frustration can be effectively relieved by lattice distortion, thus paving the way for tuning of complex magnetism in yet other 3d-5d (4d) double perovskites.

No MeSH data available.


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Lattice structures of Ca2FeOsO6 (a) and Sr2FeOsO6 (b). The Fe-O-Os paths are shown by solid lines, and experimentally measured Fe-O-Os angles are also shown in units of degrees. The Os-O-O-Os paths are depicted by dashed lines. The Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are depicted by dot-dashed lines. The in-plane and out-of-plane paths are shown in black and blue, respectively. The letter a, b and c denote the crystal axes. Ca2+ and Sr2+ ions are not displayed for the sake of clarity.
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f1: Lattice structures of Ca2FeOsO6 (a) and Sr2FeOsO6 (b). The Fe-O-Os paths are shown by solid lines, and experimentally measured Fe-O-Os angles are also shown in units of degrees. The Os-O-O-Os paths are depicted by dashed lines. The Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are depicted by dot-dashed lines. The in-plane and out-of-plane paths are shown in black and blue, respectively. The letter a, b and c denote the crystal axes. Ca2+ and Sr2+ ions are not displayed for the sake of clarity.

Mentions: As a result of spin-lattice coupling, the magnetism is usually correlated with the detailed lattice structure. Previous experiments showed that Ca2FeOsO6, SrCaFeOsO6 and Sr2FeOsO6 have somewhat different lattice distortion patterns. Ca2FeOsO6 crystallizes with a monoclinic space group of P21/n7, yet Sr2FeOsO6 crystallizes with a tetragonal symmetry2021. In the ab plane, the Fe-O-Os, Os-O-O-Os, Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths of Ca2FeOsO6 are very similar to those of Sr2FeOsO6, except that the lattice distortion in the former case is much stronger (see Fig. 1). In Ca2FeOsO6, the out-of-plane Fe-O-Os paths are very bent (see Fig. 1a). Consequently, the out-of-plane Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are highly distorted as well (see Fig. 1a). However, the out-of-plane Fe-O-Os angles in Sr2FeOsO6 are all nicely 180 degrees, and the out-of-plane Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are not at all distorted (see Fig. 1b). Compared to Ca2FeOsO6, Sr2FeOsO6 also has less distorted out-of-plane Os-O-O-Os paths. Finally, it is worth noting that SrCrFeOsO6 takes on a similar structure to Ca2FeOsO6, but with a reduced structural distortion718. Therefore, we find progressively weaker lattice distortion when comparing Ca2FeOsO6 to SrCaFeOsO6, to Sr2FeOsO6.


Lattice-distortion Induced Magnetic Transition from Low-temperature Antiferromagnetism to High-temperature Ferrimagnetism in Double Perovskites A2FeOsO6 (A = Ca, Sr).

Hou YS, Xiang HJ, Gong XG - Sci Rep (2015)

Lattice structures of Ca2FeOsO6 (a) and Sr2FeOsO6 (b). The Fe-O-Os paths are shown by solid lines, and experimentally measured Fe-O-Os angles are also shown in units of degrees. The Os-O-O-Os paths are depicted by dashed lines. The Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are depicted by dot-dashed lines. The in-plane and out-of-plane paths are shown in black and blue, respectively. The letter a, b and c denote the crystal axes. Ca2+ and Sr2+ ions are not displayed for the sake of clarity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542468&req=5

f1: Lattice structures of Ca2FeOsO6 (a) and Sr2FeOsO6 (b). The Fe-O-Os paths are shown by solid lines, and experimentally measured Fe-O-Os angles are also shown in units of degrees. The Os-O-O-Os paths are depicted by dashed lines. The Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are depicted by dot-dashed lines. The in-plane and out-of-plane paths are shown in black and blue, respectively. The letter a, b and c denote the crystal axes. Ca2+ and Sr2+ ions are not displayed for the sake of clarity.
Mentions: As a result of spin-lattice coupling, the magnetism is usually correlated with the detailed lattice structure. Previous experiments showed that Ca2FeOsO6, SrCaFeOsO6 and Sr2FeOsO6 have somewhat different lattice distortion patterns. Ca2FeOsO6 crystallizes with a monoclinic space group of P21/n7, yet Sr2FeOsO6 crystallizes with a tetragonal symmetry2021. In the ab plane, the Fe-O-Os, Os-O-O-Os, Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths of Ca2FeOsO6 are very similar to those of Sr2FeOsO6, except that the lattice distortion in the former case is much stronger (see Fig. 1). In Ca2FeOsO6, the out-of-plane Fe-O-Os paths are very bent (see Fig. 1a). Consequently, the out-of-plane Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are highly distorted as well (see Fig. 1a). However, the out-of-plane Fe-O-Os angles in Sr2FeOsO6 are all nicely 180 degrees, and the out-of-plane Fe-O-Os-O-Fe and Os-O-Fe-O-Os paths are not at all distorted (see Fig. 1b). Compared to Ca2FeOsO6, Sr2FeOsO6 also has less distorted out-of-plane Os-O-O-Os paths. Finally, it is worth noting that SrCrFeOsO6 takes on a similar structure to Ca2FeOsO6, but with a reduced structural distortion718. Therefore, we find progressively weaker lattice distortion when comparing Ca2FeOsO6 to SrCaFeOsO6, to Sr2FeOsO6.

Bottom Line: High-temperature insulating ferrimagnetism is investigated in order to further reveal its physical mechanisms, as well as identify potentially important scientific and practical applications relative to spintronics.Also discussed is the 5d(3)-3d(5) superexchange.We propose that such superexchange is intrinsically antiferromagnetic instead of ferromagnetic as previously thought.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China.

ABSTRACT
High-temperature insulating ferrimagnetism is investigated in order to further reveal its physical mechanisms, as well as identify potentially important scientific and practical applications relative to spintronics. For example, double perovskites such as Sr2FeOsO6 and Ca2FeOsO6 are shown to have puzzling magnetic properties. The former is a low-temperature antiferromagnet while the latter is a high-temperature insulating ferrimagnet. In order to understand the underlying mechanisms, we have investigated the frustrated magnetism of A2FeOsO6 by employing density functional theory and maximally-localized Wannier functions. We find lattice distortion enhances the antiferromagnetic nearest-neighboring Fe-O-Os interaction, however weakens the antiferromagnetic interactions via the Os-O-O-Os and Fe-O-Os-O-Fe paths, so is therefore responsible for the magnetic transition from the low-temperature antiferromagnetism to the high-temperature ferrimagnetism as the decrease of the A(2+) ion radii. Also discussed is the 5d(3)-3d(5) superexchange. We propose that such superexchange is intrinsically antiferromagnetic instead of ferromagnetic as previously thought. Our work clearly illustrates the magnetic frustration can be effectively relieved by lattice distortion, thus paving the way for tuning of complex magnetism in yet other 3d-5d (4d) double perovskites.

No MeSH data available.


Related in: MedlinePlus