Structure and applied-field Mössbauer studies of NiCuZn ferrite

Ni0.6Cu0.2Zn0.2Fe2O4 powder was synthesized by the solid-state reaction method. The crystal structure was found to be a cubic spinel with the lattice constant a0 of 8.373 Å and internal structure parameter (x) of the oxygen was 0.254. Ni and Cu ions in NiCuZn ferrite prefer octahedral sites B and Zn ions prefer tetrahedral sites A. Based on the distribution probability, we have analyzed Mössbauer spectra measured at 4.2 K as 5 sets with six-lines. Hyperfine fields of A and B sites at 4.2 K in zero magnetic field were Hhf(B0) = 547 kOe, Hhf(B1) = 532 kOe, Hhf(B2) = 519 kOe, Hhf(B3) = 491 kOe, and Hhf(A) = 507 kOe. Applied-field Mössbauer spectra of the Ni0.6Cu0.2Zn0.2Fe2O4 were measured with external field under 50 kOe, parallel to the incident γ-ray at 4.2 K. The hyperfine field Hhf(A) of A sites under 50 kOe was 521 kOe, larger than that under no applied-field. At B site the average value of hyperfine field 〈Hhf(B)〉 was 447 kOe, smaller than 〈Hhf(B)〉 = 522 kOe under no applied-field. Also, we noticed that the second and fifth absorption lines of Mössbauer spectra completely disappeared above 10 kOe, indicating that the spins of Fe ions at A and B sites were collinear to the applied-field. The Fe valence state was determined to be ferric from the isomer shift values.