Ballistic (precessional) contribution to the conventional magnetic switching

TL;DR

This paper investigates how a small perpendicular bias field influences the switching time of a magnetic moment under an external field, revealing a non-monotonic relationship with an optimal sweep time for faster switching.

Contribution

It provides an analytic derivation of the optimal field sweep time considering ballistic precessional effects, enhancing understanding of magnetic switching dynamics.

Findings

Switching time is non-monotonic with sweep rate, showing a minimum at an optimal point.

Analytic expressions for optimal sweep time and switching dependence are derived.

Implications for optimizing magnetic memory device performance.

Abstract

We consider a magnetic moment with an easy axis anisotropy energy, switched by an external field applied along this axis. Additional small, time-independent bias field is applied perpendicular to the axis. It is found that the magnet's switching time is a non-monotonic function of the rate at which the field is swept from "up" to "down". Switching time exhibits a minimum at a particular optimal sweep time. This unusual behavior is explained by the admixture of a ballistic (precessional) rotation of the moment caused by the perpendicular bias field in the presence of a variable switching field. We derive analytic expressions for the optimal switching time, and for the entire dependence of the switching time on the field sweep time. The existence of the optimal field sweep time has important implications for the optimization of magnetic memory devices.