Magnetic switching modes for exchange spring systems [formula omitted] with competing anisotropies

Abstract

The magnetization reversal processes of [ 10 nm ErFe 2 / n YFe 2 / 4 nm DyFe 2 / n YFe 2 ] multilayer films with a (1 1 0) growth axis and a variable YFe 2 layer thickness n are investigated. The magnetically soft YFe 2 compound acts as a separator between the hard rare earth (RE) ErFe 2 and DyFe 2 compounds, each of them bearing different temperature dependent magnetic anisotropy properties. Magnetic measurements of a system with n = 20 nm reveal the existence of three switching modes: an independent switching mode at low temperatures, an ErFe 2 spin flop switching mode at medium high temperatures, and an YFe 2 dominated switching mode at high temperatures. The measurements are in qualitative agreement with the findings of micromagnetic simulations which are used to illustrate the switching modes. Further simulations for a varied YFe 2 layer thickness n ranging from 2 to 40 nm are carried out. Quantitative criteria are defined to classify the reversal behavior, and the resultant switching modes are laid out in a map with regard to n and the temperature T . A new coupled switching mode emerges above a threshold temperature for samples with thin YFe 2 separation layers as a consequence of the exchange coupling between the magnetically hard ErFe 2 and DyFe 2 layers. It reflects the increasing competition of the two conflicting anisotropies to dominate the magnetic switching states of both RE compounds under decreasing n .