Micromagnetic examination of exchange coupled ferromagnetic nanolayers

Abstract

The aim of this paper is to give an outline of the relation between microscopic properties of a ferromagnetic triple-layer system (e.g. layer thickness, material constants) and the macroscopic magnetic properties such as nucleation field, remanent magnetisation and maximum energy product of the system. The paper concentrates on one special multilayer design, where two magnetically hard bulks are seperated by a magnetically soft interlayer with varying thickness. Depending on the thickness of the soft interlayer this system exhibits strong exchange coupling between the different magnetic phases. This exchange coupling results in complex magnetisation behaviour. The influence of the material constants of the magnetic phases and the relative layer thicknesses on the magnetic properties of the compound material are described. The results of these analytical calculations also give a qualitative information concerning the behaviour of three-dimensional grain structures. In spite of this qualitative character, however, the triple-layers discussed in this paper can be seen as a simple model of a multilayer or of an exchange coupled two-phase magnet. The investigation of the magnetic properties of this composite magnet design can, therefore, serve as a guideline for the development of more complex nanocrystalline composite magnets.