Theoretical limit of the minimal magnetization switching field and the optimal field pulse for Stoner particles

TL;DR

This paper establishes the theoretical minimum magnetic field for switching in Stoner particles, explores how optimal field pulses can minimize switching time, and reveals dependencies on damping and anisotropy.

Contribution

It provides the first theoretical limit of minimal switching field and characterizes the optimal field pulse shape for uniaxial Stoner particles.

Findings

The minimal switching field is proportional to damping in weak damping regimes.

The minimal field approaches the Stoner-Wohlfarth limit at large damping.

Optimal pulse shape depends only on damping constant.

Abstract

The theoretical limit of the minimal magnetization switching field and the optimal field pulse design for uniaxial Stoner particles are investigated. Two results are obtained. One is the existence of a theoretical limit of the smallest magnetic field out of all possible designs. It is shown that the limit is proportional to the damping constant in the weak damping regime and approaches the Stoner-Wohlfarth (SW) limit at large damping. For a realistic damping constant, this limit is more than ten times smaller than that of so-called precessional magnetization reversal under a non-collinear static field. The other is on the optimal field pulse design: If the magnitude of a magnetic field does not change, but its direction can vary during a reversal process, there is an optimal design that gives the shortest switching time. The switching time depends on the field magnitude, damping constant, and magnetic anisotropy. However, the optimal pulse shape depends only on the damping constant.