Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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   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-$\pi$ coupling between the
down-spin Re$^{5+}$/Fe$^{3+}$ $t_{2g}$ orbitals via the intermediate O
$2p_{\pi}$ ones, also a very similar FiM and HM state of Sr$_{2}$FeMoO$_{6}$.
In contrast, a decreasing Fe $t_{2g}$ component at Fermi level ($E_{F}$) in the
distorted Ca$_{2}$FeReO$_{6}$ partly accounts for its nonmetallic behavior,
while a finite $pdd$-$\sigma$ 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$^{3+}$
$t_{2g}$ 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.

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The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
2
The categories of this paper are: math
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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas