Rare-Earth-Transition Metal-Base Alloys
Amorphous ferromagnetic alloys can be divided into several groups; among them are: transition metal–metalloid base alloys and rare-earth-transition metal (RE-TM) base alloys. Anisotropic microstructures, accompanying spatial variation in magnetization, can also produce effective magnetic anisotropics. In many cases, the magnetization is significantly reduced by exchange fluctuations and the materials generally possess low coercivity and no magnetic anisotropy. The uniaxial anisotropy must be due to slight deviation from the isotropic random distribution of atoms; such anisotropic distribution can be due to nonspherically symmetric preparation conditions. In general, anisotropy in magnetic materials can arise from several sources: magnetic crystalline, stress, shape dipolar interaction, and short-range ordering. Applications for RE-TM bulk alloys include thermomagnetic information storage,7 as precursor materials for the preparation of permanent magnets," and contact printing. Briefly stated, a magnetic bubble is in fact cylindrical in shape; it represents a region of reversed magnetization in a magnetic material.