Hysteresis in Layered Spring Magnets

TitleHysteresis in Layered Spring Magnets
Publication TypeReport
Year of Publication2001
AuthorsJiang, JS, Kaper, HG, Leaf, GK
Series TitleDiscrete and Continuous Dynamical Systems-Series B
Date Published01/2001
Other NumbersANL/MCS-P867-0101

This article addresses a problem of micromagnetics: the reversal of magnetic moments in layered spring magnets. A one-dimensional model is used of a film consisting of several atomic layers of a soft material on top of several atomic layers of a hard material. Each atomic layer is taken to be uniformly magnetized, and spatial inhomogeneities within an atomic layer are neglected. The state of such a system is described by a chain of magnetic spin vectors. Each spin vector behaves like a spinning top driven locally by the effective magnetic field and subject to damping (Landau-Lifshitz-Gilbert equation). A numerical integration scheme for the LLG equation is presented that is unconditionally stable and preserves the magnitude of the magnetization vector at all times. The results of numerical investigations for a bilayer in a rotating in-plane magnetic field show hysteresis with a basic period of 2pat moderate fields and hysteresis with a basic period of p at strong fields.