Scaling of Coercivity in a 3d Random Anisotropy Model

TL;DR

This paper investigates how coercivity scales in a large-scale 3D random anisotropy model, revealing power-law relationships that inform the design of magnetic materials.

Contribution

It provides numerical and theoretical analysis of coercivity scaling in a 3D random anisotropy Heisenberg model, with implications for magnetic material design.

Findings

Coercive field scales as the fourth power of anisotropy strength.

Coercive field scales as the sixth power of grain size.

Numerical results are supported by theoretical explanations.

Abstract

The random-anisotropy Heisenberg model is numerically studied on lattices containing over ten million spins. The study is focused on hysteresis and metastability due to topological defects, and is relevant to magnetic properties of amorphous and sintered magnets. We are interested in the limit when ferromagnetic correlations extend beyond the size of the grain inside which the magnetic anisotropy axes are correlated. In that limit the coercive field computed numerically roughly scales as the fourth power of the random anisotropy strength and as the sixth power of the grain size. Theoretical arguments are presented that provide an explanation of numerical results. Our findings should be helpful for designing amorphous and nanosintered materials with desired magnetic properties.