How the structure of ferromagnetic cluster boundaries in an antiferromagnetic matrix impacts their magnetic properties in an external field

Abstract

The question of how an external field impacts the magnetic moments of ferromagnetic clusters that are randomly located in a thin cylinder, is considered. The clusters have a magnetic dipole interaction. If there is sufficient spatial anisotropy, such a system can be described by a one-dimensional Ising model with a random exchange if an effective local field is present. A random effective field acting on the clusters reflects the inhomogeneity of the interface between the clusters and the antiferromagnet. In fields smaller than the saturation field, the ground state of such a model is a one-dimensional sequence of domains having different lengths. In contrast to the one-dimensional Ising model, at a constant field in the presence of a random effective field, there is a linear dependence of magnetization on the external field, in the small field region. The average of the random effective field determines the magnitude of the magnetization curve exchange bias, and the dispersion of the random effective field affects its slope. The results obtained in this study, together with experimental data, allow for a qualitative evaluation of the properties of the interface between the subsystems.