Structure and Mossbauer studies of Cu-doped Ni-Zn ferrite

Ni0.65Zn0.35 CuxFe2-xO4 (x = 0.0-0.3) was studied with X-ray diffraction, M ossbauer spectroscopy and vibrating sample magnetometer (VSM). The crystal structure was found to be a cubic spinel, and the lattice constants increas ed linearly with increasing quantity of Cu ions with the lattice constant a (0) = 8.384 +/- 0.005 Angstrom at x = 0.0. Mossbauer spectra of Ni0.65Zn0.3 5CuxFe2-xO4 (x = 0.0-0.3) were taken at various temperatures ranging from 1 2 to 725 K. As the temperature increased toward TN,a systematic line broade ning effect in the Mossbauer spectra was observed and was interpreted as or iginating from different temperature dependencies of the magnetic hyperfine fields at various iron sites. The isomer shifts indicated that the iron io ns were ferric at the tetrahedral CAI and the octahedral sites CBI. The qua drupole shifts showed that the orientation of the magnetic hyperfine field with respect to the principal axes of the electric field gradient was rando m. The magnetic hyperfine field values indicated that A sites had more A-O- B superexchange interactions than the B sites. The Neel temperature decreas ed with increasing quantity of Cu ions with T-N = 725 +/- 2 K at x = 0.0. A lso, the Debye temperatures of the A and B sites of Ni0.65Zn0.35CU0.1Fe1.9O 4 were found to be Theta(A) = 278 +/- 5 K and Theta(B) = 328 +/- 5 K. The V SM data showed that the magnetic moment decreased with increasing quantity of Cu ions with magnetic moment and coercivity values of M-s = 66 emu/g and H-c = 36 Oe at x = 0.3. (C) 2000 Elsevier Science B.V. All rights reserved .