Switching time of a single spin in linearly varying field

Abstract

We studied the switching time of a single spin in a field varying linearly in time using a micromagnetics simulation based on the Landau-Lifshitz-Gilbert equation. The applied field larger than the switching field or coercivity is not enough for a spin to switch but some duration of time is also necessary. We found that the value of C 1 defined by C 1= (H - H 1) dt was constant when the rate of change in the field was larger than 10× γH k2, where γ is the gyromagnetic ratio with g value = 2, H is the applied field, H 1 is a constant, and H k is the anisotropy field of the spin. The integration is taken from the time the spin begins switching to the switching time. The equation is a generalized form of the equation, C 0 (H - H 0)τsw, in a constant field H. Here, C 0 and H 0 are constants, and τ sw is the switching time. We found that C 1 in the region dH/dt >10 ×γH K2 and C 0 in the region H≫H K are the same, but that H 1 does not coincide with H 0. We found that the head field rise time has a very small effect on the switching field and time of recording media. © 2012 American Institute of Physics.