Electronic structure study of double perovskites $A_{2}$FeReO$_{6}$ (A=Ba,Sr,Ca) and Sr$_{2}M$MoO$_{6}$ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U

Hua Wu

doi:10.1103/PhysRevB.64.125126

paper

Electronic structure study of double perovskites $A_{2}$ FeReO $_{6}$ (A=Ba,Sr,Ca) and Sr $_{2} M$ MoO $_{6}$ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U

arXiv:cond-mat/0107462 · doi:10.1103/PhysRevB.64.125126

Abstract

We have implemented a systematic LSDA and LSDA+U study of the double perovskites $A_{2}$ FeReO $_{6}$ (A=Ba,Sr,Ca) and Sr $_{2}$ $M$ MoO $_{6}$ (M=Cr,Mn,Fe,Co) for understanding of their intriguing electronic and magnetic properties. The results suggest a ferrimagnetic (FiM) and half-metallic (HM) state of $A_{2}$ FeReO $_{6}$ (A=Ba,Sr) due to a pdd- $π$ coupling between the down-spin Re $^{5 +}$ /Fe $^{3 +}$ $t_{2 g}$ orbitals via the intermediate O $2 p_{π}$ ones, also a very similar FiM and HM state of Sr $_{2}$ FeMoO $_{6}$ . In contrast, a decreasing Fe $t_{2 g}$ component at Fermi level ( $E_{F}$ ) in the distorted Ca $_{2}$ FeReO $_{6}$ partly accounts for its nonmetallic behavior, while a finite $p dd$ - $σ$ coupling between the down-spin Re $^{5 +}$ /Fe $^{3 +}$ $e_{g}$ orbitals being present at $E_{F}$ serves to stabilize its FiM state. For Sr $_{2}$ CrMoO $_{6}$ compared with Sr $_{2}$ FeMoO $_{6}$ , the coupling between the down-spin Mo $^{5 +}$ /Cr $^{3 +}$ $t_{2 g}$ orbitals decreases as a noticeable shift up of the Cr $^{3 +}$ 3d levels, which is likely responsible for the decreasing $T_{C}$ value and weak conductivity. Moreover, the calculated level distributions indicate a Mn $^{2 +}$ (Co $^{2 +}$ )/Mo $^{6 +}$ ionic state in Sr $_{2}$ MnMoO $_{6}$ (Sr $_{2}$ CoMoO $_{6}$ ), in terms of which their antiferromagnetic insulating ground state can be interpreted. While orbital population analyses show that owing to strong intrinsic pd covalence effects, Sr $_{2} M$ MoO $_{6}$ (M=Cr,Mn,Fe,Co) have nearly the same valence state combinations, as accounts for the similar M-independent spectral features observed in them.

21 pages, 3 figures. to be published in Phys. Rev. B on 15th Sep

References in corpus (1)

Strong ferromangnetism and weak antiferroamgnetism in double perovskites: Sr $_{2}$ Fe{/it M}O $_{6}$ ({/it M}=Mo, W and Re)

Electronic structure study of double perovskites A2​FeReO6​ (A=Ba,Sr,Ca) and Sr2​MMoO6​ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U

Abstract

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Electronic structure study of double perovskites $A_{2}$ FeReO $_{6}$ (A=Ba,Sr,Ca) and Sr $_{2} M$ MoO $_{6}$ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U