Design of soft magnetic materials

TL;DR

This paper introduces a micromagnetic design strategy for creating ferromagnetic materials with very low coercivity, validated by solving the Permalloy Problem and offering new insights into magnetic material properties.

Contribution

The paper develops a novel micromagnetic algorithm-based design approach predicting low coercivity cubic materials with specific magnetostriction and anisotropy properties, advancing magnetic material design.

Findings

Predicts low coercivity in cubic materials with specific property tuning.

Provides an explicit dimensionless criterion for low coercivity.

Validates the approach by solving the Permalloy Problem.

Abstract

We present a strategy for the design of ferromagnetic materials with exceptionally low magnetic hysteresis, quantified by coercivity. In this strategy, we use a micromagnetic algorithm that we have developed in previous research and which has been validated by its success in solving the "Permalloy Problem" -- the well-known difficulty of predicting the composition 78.5% Ni of lowest coercivity in the Fe-Ni system -- and by the insight, it provides into the "Coercivity Paradox" of W. F. Brown. Unexpectedly, the design strategy predicts that cubic materials with large saturation magnetization $m_s$ and large magnetocrystalline anisotropy constant $\kappa_1$ will have low coercivity on the order of that of Permalloy, as long as the magnetostriction constants $\lambda_{100}, \lambda_{111}$ are tuned to special values. The explicit prediction for a cubic material with low coercivity is the dimensionless number $(c_{11}-c_{12}) \lambda_{100}^2/\kappa_1 = 81$ for $\langle 100 \rangle$ easy axes. The results would seem to have a broad potential application, especially to magnetic materials of interest in energy research.