Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superexchange in Dilute Magnetic Dielectrics: Application to (Ti,Co)O_2   We extend the model of ferromagnetic superexchange in dilute magnetic
semiconductors to the ferromagnetically ordered highly insulating compounds
(dilute magnetic dielectrics). The intrinsic ferromagnetism without free
carriers is observed in oxygen-deficient films of anatase TiO_2 doped with
transition metal impurities in cation sublattice. We suppose that ferromagnetic
order arises due to superexchange between complexes [oxygen vacancies +
magnetic impurities], which are stabilized by charge transfer from vacancies to
impurities. The Hund rule controls the superexchange via empty vacancy related
levels so that it becomes possible only for the parallel orientation of
impurity magnetic moments. The percolation threshold for magnetic ordering is
determined by the radius of vacancy levels, but the exchange mechanism does not
require free carriers. The crucial role of the non-stoichiometry in formation
of the ferromagnetism makes the Curie temperatures extremely sensitive to the
methods of sample preparation.

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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
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The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: hep-th