Magnetic hysteresis properties of BaFe12−xInxO19 ceramic ferrites with c‐axis oriented grains

To study the effects of reduced magnetic anisotropy on hysteresis loops of hard magnets for possible use in self‐biased microwave devices, a new family of magnetically oriented (c‐axis) In‐substituted Ba ferrite was prepared by conventional ceramic techniques. Earlier studies of BaFe12−x(In,Sc)xO19 series in single‐crystal form have shown that magnetization 4πM and anisotropy field Hk decrease sharply with increasing x. Since hysteresis loops with optimum energy products require uniformly small grains (1 to 3 μm), sintering temperatures were carefully controlled over a range from 1180 to 1075 °C for 2 h, depending on In content. For nominal values of x ranging from 0 to 1.5, square hysteresis loops with Hc values decreasing from 3500 to 150 Oe were recorded with a high‐field hysteresisgraph. The effective Hk values were measured and compared with single‐crystal data to estimate the degree of grain alignment for each composition.