Mössbauer Study of Copper Ferrites

Abstract

Tetragonal and cubic CuFe2O4 are prepared and studied by Mössbauer‐effect technique at room temperature and at 4.2 K with and without applied strong magnetic fields. The cation distributions and the hyperfine parameters are determined and compared with magnetization measurements. The results show that tetragonal CuFe2O4 is an inverse spinel of Néel collinear arrangement of spins and that cubic copper ferrite is not completely inverse with a cation distribution dependent on the heat treatment.

Cation Migration and Coercivity in Mixed Copper–Cobalt Spinel Ferrite Powders

“…The spinel lattice is thus highly distorted (c/a&1.06) because of a cooperative Jahn-Teller effect arising from the octahedral cupric ions (4,5). Part of the Cu> ions can be frozen in tetrahedral sites when the ferrites are quenched in air from temperatures higher than 400°C (1,3,6,7). The resulting ferrites show a smaller tetragonal distortion since a great proportion of the cupric ions are located on tetrahedral sites.…”

“…Close to thermodynamic equilibrium at room temperature, the copper ferrites may be described by the structural formula Fe> [Fe>Cu>]O\ , in which the octahedral cations are placed inside square brackets (1)(2)(3). The spinel lattice is thus highly distorted (c/a&1.06) because of a cooperative Jahn-Teller effect arising from the octahedral cupric ions (4,5).…”

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

“…Recent studies showed that the cation distribution in a cubic CuFe 2 O 4 can be given as ðCu x Fe 1Àx Þ T d ½Cu 1Àx Fe 1þx O h O 4 ; in which the parentheses and square brackets denote tetrahedral and octahedral sites, respectively, whereas tetragonal CuFe 2 O 4 is completely inverse, i.e., x ¼ 0 [5,6]. The ground state of Cu 2þ ion in the octahedral crystal field is an orbital doublet 2 E g ðt 6 2g e 3 g Þ and so subject to a Jahn-Teller effect which removes the degeneracy of the ground state.…”

M�ssbauer Studies of Superexchange Interaction in Tetragonal CuFe2O4

“…Its lattice parameters are a 0 5.873 # e and c 0 8.555 # e. Its metallic atoms are in an inverse distribution [1,2]; half the atoms of iron are in the A (tetrahedral) sites and the other half plus the copper atoms in the B (octahedral) sites: Fe A CuFe B O 4 . When preparations of this compound are rapidly quenched from above 760 C, they are cubic with the unit a 0 8.383 # e.…”