Laminated soft magnetic materials

Abstract

Soft magnetic materials such as Permalloy can be laminated with nonmagnetic spacers in such a way as to eliminate all, or almost all, of the domain walls in a small element. This has the potential to increase permeance and reduce noise in devices such as recording head yokes. Laminations for this purpose need to have even numbers of magnetic layers, with spacers thick enough to prevent exchange interaction between the magnetic layers, which are then magnetostatically coupled. In the desired 'easy-axis' state (M ∥ the magnetic easy axis), 'edge-curling' regions occur along edges not parallel to the magnetic easy axis. Edge-curling regions can lead to instabilities, noise, and even (if too wide) to M being oriented along the hard axis. Conditions for controlling magnetic state and edge-curling region width, and the implications for stability are discussed.