Inter-grain tunneling in the half-metallic double-perovskites Sr$_2$BB'O$_6$ (BB'-- FeMo, FeRe, CrMo, CrW, CrRe

Structural and metal-insulator transitions in rhenium based double perovskites via orbital ordering

Re-based double perovskites (DPs) exhibit a complex interplay of structural and metal-insulator transitions. Here we systematically study the ground state electronic and structural properties for a family of Re-based DPs $A_2B$ReO$_6$ ($A$=Sr, Ca and $B$=Cr, Fe), which are related by a common low energy Hamiltonian, using density functional theory + $U$ calculations. We show that the on-site interaction $U$ of Re induces orbital ordering (denoted COO), with each Re site having an occupied $d_{xy}$ orbital and a C-type alternation among $d_{xz}/d_{yz}$, resulting in an insulating state consiste…

LSDA和LSDA +U合成双钙钛矿$A_{2}$ FeReO PDMATHAAC（A=Ba，Sr，Ca）和Sr $_{2}M$ MoO $_{6}$（M=Cr，Mn，Fe，Co）的电子结构研究

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

我们对双钙钛矿$A_{2}$ FeReO $_{6}$（A=Ba，Sr，Ca）和SrPDMATHABMO $M$ MoO $_{6}$（M=Cr，Mn，Fe，Co）进行了系统的LSDA和LSDA+U研究，以了解它们有趣的电子和磁性。结果表明，由于下自旋Re $^{5+}$ /Fe $t_{2g}$ $t_{2g}$轨道通过中间O $2p_π$轨道发生pdd-$π$耦合，$A_{2}$ FeReO $_{6}$（A=Ba，Sr）具有亚铁磁（FiM）和半金属（HM）态，Sr $_{2}$ FeMoO $_{6}$也具有非常相似的FiM和HM态.相反，在畸变的Ca $_{2}$ FeRe O $_{6}$中，费米能级处Fe $t_{2g}$分量（$E_{F}$）的减少部分地解释了其非金属行为，而在$E_{F}$处存在的下自旋Re $^{5+}$ /Fe $^{3+}$ $e_{g}$轨道之间的有限$pdd$-$σ$耦合用于稳定其FiM状态。对于Sr $_{2}$ CrMoO $_{6}$与Sr $_{2}$ FeMoO $_{6}$相比，下自旋Mo $^{5+}$ /Cr $^{3+}$ $t_{2g}$轨道之间的耦合随着Cr $^{3+}$ 3d能级的显著上移而降低，这可能是导致$T_{C}$值降低和导电性弱的原因。此外，计算的能级分布表明，在Sr $_{2}$ MnMoO $_{6}…