A 3D anisotropic rotation model for magnetization and magnetostriction in Tb0.3Dy0.7Fe1.9 (abstract)

Abstract

The highly magnetostrictive alloy Tb0.3Dy0.7Fe1.9 orders with its magnetic moments aligned along the 〈111〉 axes. When a magnetic field is applied along one of the 〈112〉 axes it has been shown in recent work that the principal magnetization mechanism is domain rotation. In order to produce higher magnetostriction at lower field strengths the initial domain orientations should be configured with high population of the [1̄1̄1] and [111̄] axes at right angles to the field direction. This paper is concerned with the determination of these population densities from magnetization and magnetostriction data using the domain rotation model in the presence of anisotropy. We have developed a three-dimensional anisotropy model for the domain rotation mechanism.1 This enables the direction of magnetization of domains originating along each of the 〈111〉 axes to be found as a function of magnetic field. The change in magnetization ΔM is calculated from: ΔM=∑piMs(cos θi − cos Ωi), where Ms is the saturation magnetization, Ωi is the initial orientation of a domain with respect to the field, and θi is the final orientation. The change in magnetostriction is calculated from: Δλ =3/2λ100Σi[(cos2 θf,j −cos2 θi,j)cos2 φj]Δλ= 3/232λ100Σi [(cos2 θf,j−coscos2 θi,j)cos2 φj] +3λ111Σ3j=1[(cos θf,j cos θf,j+1 −cos θi,j cos θi,j+1)cos φj cos φj+1]pi. The population densities pi of the domain in the various 〈111〉 axial directions determine the amplitude of the magnetostriction. From the model it is possible to determine the bulk magnetization and magnetostriction from the occupancies of these directions.<ks>