Structural and magnetic properties of holmium substituted cobalt ferrites synthesized by chemical co-precipitation method

摘要

CoHo_xFe_(2-x)O_4 ferrites (x=0.00-0.1) were prepared by the co-precipitation technique and the effect of holmium substitution on the magnetic properties was investigated. X-ray diffraction reveals that the substituted samples show a second phase of HoFeO_3 along with the spinel phase. The magnetic properties such as the saturation magnetization (M_s), coercivity (H_c) and remanence (M_r) are obtained from the hysteresis loops. It is observed that the M_s decreases while H_c increases with Ho~(3+) substitution. The decrease of saturation magnetization is attributed to the weakening of exchange interactions. The coercivity increases with increase of the Ho~(3+) concentration, which is attributed to the presence of an ultra-thin layer at the grain boundaries that impedes the domain wall motion. Low field AC susceptibility was also measured over the temperature range 300-600 K at the frequency of 200 Hz. It decreases with the increase of temperature following the Curie-Weiss law up to the Curie temperature. Above the Curie temperature it shows paramagnetic behavior. The increase in coercivity suggests that the material can be used for applications in perpendicular recording media.