X-RAY AND BULK MAGNETIC-PROPERTIES OF ALUMINUM SUBSTITUTED FERRITES

The compositions having the general formula Ni0.55Zn0.45AltFe2-tO4 and Ni0.65Zn0.35AltFe2-tO4 with t = 0.0, 0.1, 0.2, 0.3 have been prepared by the standard ceramic technique and sintered at 1100, 1150, 1200 an d 1240 degrees C to attain different microstructures. The lattice para meter a, magnetization M(s) are seen to decrease with increasing Al3content whereas the coercive force H-c shows an increasing trend with Al3+ content. M(s) is found to be invariant with the changes in sinter ing temperature. The coercivity H-c and the remanent ratio R = M(R)/M( S) are seen to depend on the sintering temperature and hence on the gr ain size D. The anisotropy field H-K(A) increases with increase of alu minium content. M(s) and H-K(A) enable calculation of the anisotropy f ield constant K-l which decreases with increase of Al3+. The compositi onal, thermal and microstructural variations of hysteresis parameters like M(s), H-c and R reveal that grains in the compositions investigat ed are of multidomain (M-D) type. This result is supported by ac susce ptibility data.