Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orbital order and ferrimagnetic properties of the new compound $Sr_8 Ca
  Re_3 Cu_4 O_{24}$   By means of the LSDA+U method and the Green function method, we investigate
the electronic and magnetic properties of the new material of
Sr$_8$CaRe$_3$Cu$_4$O$_{24}$. Our LSDA+U calculation shows that this system is
an insulator with a net magnetic moment of 1.01 $\mu_{\rm B}$/f.u., which is in
good agreement with the experiment. Magnetic moments are mainly located at Cu
atoms, and the magnetic moments of neighboring Cu sites align anti-parallel. It
is the non-magnetic Re atoms that induce an orbital order of $d$ electrons of
Cu atoms, which is responsible for the strong exchange interaction and the high
magnetic transition temperature. Based on the LSDA+U results, we introduce an
effective model for the spin degrees of freedom, and investigate the
finite-temperature properties by the Green function method. The obtained
results are consistent with the experimental results, indicating that the
spin-alternating Heisenberg model is suitable for this compound.

25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an