Study of magnetic properties in Ni-Mn ferrites by Moessbauer spectroscopy

Ni/sub 1-x/Mn/sub x/Fe/sub 2/O/sub 4/ (x=0, 0.25, 0.50, 0.75, 1.0) ferrites have been studied at room temperature using the Moessbauer effect. In these ferrites the internal magnetic field (H/sub eff/) decreases with the increase of Mn. For tetrahedral site (A-site) it shows a small decrease with x(mn) but for octahedral site (B-site) the magnetic field varies in three steps. In initial stage it shows small decrease, sharp decrease in the intermediate stage while gain small decease in the final stage. The line width of the Moessbauer spectra shows a linear increase for B-sites while sigmoidal behaviour for A -site. The quadrupole splitting is almost zero in all compositions for both sites. The isomer shift remains constant for both sites in all composites except for x-=0.50. It shows sudden increase for B-site and same type of decrease for A- site. The area ratio (A/B) decreases with x. (author)