Mossbauer studies of Ti-x(Fe(2-2x)M(1+x))O-4 and Ge-x(Fe(2-2x)M(1+x))O-4 (M=Co and Ni)

Four ferrite systems have been prepared by the ceramic method. The investigated systems are Ti-x(Fe(2-2x)M(1+x))O-4 and Ge-x(Fe(2-2x)M(1+x))O-4, M = Co and Ni, where x = 0.25 and 0.5 for Ge-x(Fe(2-2x)M(1+x))O-4 and x = 0.25, 0.5, and 0.75 for Ti-x(Fe(2-2x)M(1+x))O-4. The obtained Mossbauer spectra reveal the presence of magnetic hyperfine interaction in all samples except for Ti0.75Co1.75Fe0.5O4. It was observed also that all Mossbauer parameters magnetic hyperfine field, quadrupole splitting, and isomer shift, depend on x. However, the estimated parameters show different dependence on x. In all cases the magnetic hyperfine field H-hf decreases with increasing x except that of TixNi1+xFe2-2xO4, where H-hf increases for x = 0.75. The obtained results have been discussed in the frame of current theories.