Local Magnetic Properties of Spinel Cd 0.9 M 0.1 Fe 2 O 4 (M = Zn, Ni) Investigated by Using External Magnetic Field M¡§ossbauer Spectrometry

Cd0.9M0.1Fe2O4 (M = Zn, Ni) ferrites, prepared by using a solid state reaction method, have been studied by using X-ray diffraction and Mossbauer spectroscopy. The lattice constants are determined to be a(o) = 8.686 angstrom for Cd0.9Zn0.1Fe2O4 and 8.664 angstrom for Cd0.9Ni0.1Fe2O4 with a cubic spinel structure. Zero-field Mossbauer spectra of the samples were taken at various temperatures ranging from 4.2 to 295 K. A line broadening arising from the relaxation effect was observed at temperatures below the Neel temperature (T-N), which is 18 K for Cd0.9Zn0.1Fe2O4 and 40 K for Cd0.9Ni0.1Fe2O4. The magnetic hyperfine fields, obtained by fitting Mossbauer spectra with two magnetic components, of Cd0.9Zn0.1Fe2O4 and Cd0.9Ni0.1Fe2O4 were H-hf(A) = 461 kOe, H-hf(B) = 492 kOe, and H-hf(A) = 485 kOe, H-hf(B) = 503 kOe, respectively. The isomer shift delta values at room temperature were 0.24 similar to 0.25 mm/s, indicating that the valence state of Fe ions is ferric in tetrahedral and octahedral coordination. Their magnetic behaviors at low temperatures were also investigated with an external-field Mossbauer spectrometer at 48 kOe and showed localized spincanting at both A and B sites with the average canting angles of 65 degrees and 54 degrees for Cd0.9Zn0.1Fe2O4 and of 51 degrees and 43 degrees for Cd0.9Ni0.1Fe2O4 at 4.2 K.