Magneto Elasticity in Amorphous Ferromagnets

Abstract

The appearance of amorphous metallic alloys in the sixty’s gave rise to new trends in magnetoelasticity1 . While local magnetic anisotropy is averaged out in most cases, as a consequence of the lack of long range order, magnetostriction and magnetoelastic effects (which are related to the stress derivative of the magnetic anisotropy) are not, and have values comparable to their crystalline counterparts. The combination of zero anisotropy and relatively large magnetoelastic coefficients make amorphous alloys very interesting both from the viewpoint of the basic science, and as potential materials for technical applications. While a number of different possibilities for amorphous ferromagnetism to appear exist, we shall focus mainly on amorphous alloys of the kind TM100-X Mx (where TM stands for one or several transition metals including ferromagnetic atoms, M is a combination of metalloids and X is around 20 at % like in Fe80B20) and a few ETM-LTM (ETM = Early Transition Metal, LTM = Late transition Metal like FeZr or FeHf) prepared by rapid cooling from the melt, i.e. the so called metallic glasses. Other alloys prepared as thin films and Rare Earth containing amorphous alloys2 will not be treated here.