Magnetostatic interaction mechanisms in a two-dimensional composite magnet

Abstract

The magnetization structure and the mechanisms of magnetic interaction in an artificial two-phase magnet are analyzed with magnetic force microscopy and magnetooptics. A model system built up of arrays of hard magnetic CoPt squares (5 μm edge length) embedded in a soft magnetic permalloy matrix is investigated. Special emphasis is put on the characterization of the matrix magnetization and on the interaction between the matrix and the CoPt squares. Different effects on different length scales are observed. At large distances to the hard magnetic dots, the magnetization of the matrix relaxes and is dominated by the characteristic pattern of an antidot array. The stability of this pattern with respect to magnetic fields and its dependence on the magnetic history of the system is analyzed. Nearby the dots, the magnetostatic coupling between the matrix and the CoPt induces a fine scale modulation of the magnetization of the matrix. At inter-dot distances up to 1 μm, the dot matrix interaction is prevalent and the matrix contributes essentially to the dot-dot interaction. We have studied the characteristics of this modulation, particularly considering their decay length and the interaction transfer mediated by the modulation.