Energy surface model of single particle reversal in sub-Stoner–Wohlfarth switching fields

Abstract

A simple energy surface model is introduced to explain single domain particle switching under sub-Stoner–Wohlfarth fields. The criterion is that if the initial energy exceeds the subsequent energy barrier maximum, then the particle can reverse. Reversal will occur only for small damping constants and short field rise times, so the magnetization dynamics explores a sufficiently large portion of the energy surface. The results are confirmed by micromagnetic analyses and are consistent with both large scale micromagnetic simulation and experimental data. This effect may be utilized for ultrahigh density (1 Tbit/in2) and ultrahigh data rate magnetic recording (>2 Gbit/s).

Fast switching in single-domain particles with uniaxial quartic anisotropy

“…2). Clearly, the threshold of the dynamic switching field for the presence of K 2 is smaller than the SW criterion for small damping constants, as previous reports for a SW particle (K 2 ¼ 0) [5,6]. For the field directions within the fast switching regime, the 'precessional' magnetization switching is dominated and the magnetization can cross over the hard plane during the first precession cycle.…”

Mapping orientations of easy axes in nanodot arrays by magnetic force microscopy

“…A magnetic dot, whose magnetizations exhibit either preferential or random orientations, should show a single-domain structure, and thus, should have an effective easy axis if its size was sufficiently small. [4][5][6] Kikuchi et al 7 and Gao et al 8 have studied this type of dependence for a sole magnetic particle by using an anomalous Hall-effect measurement and a theoretical calculation, respectively. Gomez et al 6 have investigated a dispersion of easy axes in a cobalt array with in-plane random orientations of easy axes by means of magnetic force microscopy (MFM).…”

Precessional Magnetization Reversal in Composite Patterned Media: Dependence on Applied Field Parameters

“…Under precessional reversal, the system can by-pass the energy barrier as long as the energy maximum is below the energy before the external field is applied, which results in a reduced reversal field [10], [11]. PR is obtained under the following three conditions: the external field is applied at an angle to the element's easy axis, the rise time is small, and the material damping constant is small [8], [11], [12].…”