Magnetic Hysteresis Properties of BaFe(12-x)In(x)O19 Ceramic Ferrites with C-AxisOriented Grains

摘要

To study the effects of reduced magnetic anisotropy on hysteresis loops of hardmagnets 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 BaFel2-x(In,Sc)xO19 series in single-crystal form have shown that magnetization 4 pi M and anisotropy field Hk decrease sharply with increasing x. Since hysteresis loops with optimum energy products require uniformly small grains (1 to 3 um), sintering temperatures were carefully controlled over a range from 1180 to 1075 deg C for 2 h, depending on In content. For nominal values of x ranging from 0 to 1.5, square hysteresis loops with H, 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.