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Magneto-optical investigation of spinel ferrite CuFe2O4: observation of Jahn–Teller effect in Cu2+ ion

2004; Elsevier BV; Volume: 279; Issue: 2-3 Linguagem: Inglês

10.1016/j.jmmm.2004.01.078

1873-4766

Kwang Joo Kim, Jung Han Lee, Sung Ho Lee,

Multiferroics and related materials

Magneto-optical properties of spinel ferrite CuFe2O4 have been investigated in comparison with those of isostructural Fe3O4. The Kerr angle and ellipticity of the ferrites were measured by magneto-optic Kerr effect spectroscopy in the 1.5–5eV region. It is found that a strong 2.1-eV absorption peak for Fe3O4, due to a d–d intervalence charge-transfer (IVCT) transition in the octahedral sites, Fe2+(t2g)→Fe3+(eg), disappears for CuFe2O4. It gives an evidence that the octahedral Fe2+ sites are well substituted by Cu2+ ions in CuFe2O4. Absorption structures at about 2.5, 3.5, and 3.9eV observed for both CuFe2O4 and Fe3O4 are assigned to inter-sublattice charge-transfer transitions between the tetrahedral and the octahedral Fe3+ ions. Two peaks observed at about 4.3 and 4.7eV for CuFe2O4 are interpreted as due to Jahn–Teller-coupled IVCT transitions, Cu2+(eg)→Fe3+(t2g), in the octahedral sites. The structure at about 1.8eV observed for CuFe2O4 is attributable to Jahn–Teller-coupled d–d crystal-field transitions, 2Eg→2T2g, in the octahedral Cu2+ ion.