Mössbauer Studies on (Zn, Cd, Cu)_0.5Ni_0.5Fe₂O₄ Oxides

Abstract

The temperature dependence of the magnetic hyperfine fields on ⁵⁷Fe nuclei at the tetrahedral (A) and octahedral (B) interstitial sites in (Zn, Cd, Cu)_0.5Ni_0.5Fe₂O₄ oxides have been investigated in Mössbauer measurements at sample temperatures ranging from 79 K to 850 K. The samples were prepared by solid-state reaction, and their phase determined from XRD measurements, which also provided information on their X-ray densities, grain sizes and lattice constants. The magnetic transition temperatures between ordered and paramagnetic states were obtained from zero-velocity measurements. The Cu_0.5Ni_0.5Fe₂O₄ sample is found to be antiferromagnetic with Néel temperature of 823 K, and its super-exchange interactions, J _AB, J _AA and J _BB were determined to be −24.14 k_B, −13.10 k_B and +11.68 k_B, respectively. The (Zn, Cd)_0.5Ni_0.5Fe₂O₄ are ferrimagnetic with Curie points of 543 and 548 K, respectively, and corresponding average exchange integrals J _o = 186 k_B and 188 k_B.