Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strong magneto-optical effects in ACr2O4 A=Fe, Co spinel oxides
  generated by tetrahedrally coordinated transition metal ions   Magneto-optical effects have been investigated over the infrared{visible
spectral range in ACr2O4 (A = Fe, Co) spinel oxides with non-collinear spin
orders in their ground states. We found large magneto-optical Kerr rotation and
ellipticity at the on-site d-d transitions of the A2+ ions located within the
charge gap. The magneto-optical Kerr rotation of 12 deg observed in CoCr2O4 is
unprecedentedly large among magnetic semiconductors and points towards the
uniqueness of tetrahedrally coordinated Co2+ ions in generating a strong
magneto-optical response. Criteria of strong magneto-optical effects emerging
at on-site d-d transitions of transition metal ions are discussed.

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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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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: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: econ