Effect of thermal fluctuations on switching field of deep submicron sized soft magnetic thin film

Abstract

In this article, the effect of thermal fluctuations on switching field at short and long time scales have been investigated by micromagnetic simulation with the Langevin and the time-temperature scaling methods. When the film thickness and/or the aspect ratio are reduced, the switching field decreases substantially owing to the decrease of shape anisotropy and the increase of thermal fluctuation. In the soft magnetic film with a dimension of 0.4 μm×0.2 μm×1 nm, the calculated switching field at a pulse width of 10 ns is 32 Oe, but estimated retention time is less than 1000 s. In such a thermally unstable film, thermally activated switching of magnetization occurs by complex behaviors with creations and annihilations of small and slightly tilted magnetic clusters.

Heat Assisted Magnetization Reversal on Perpendicular Magnetized Nano-Dot

“…An approximation of thermal fluctuation effect occurring during magnetization is taken into account by involving randomly oriented effective fields with zero mean value,H  eff (t)=0. Whereas, strength of the random field due to the thermal fluctuation effect is calculated by using a fluctuation dissipation theorem [7]:…”

Low Writing Field on Perpendicular Nano-ferromagnetic

“…Micromagnetic simulation for thermally assisted magnetization reversal evaluation has been performed using the modified micromagnetic simulator created by H. Takamatsu, ), V = volume of media, M s = magnetic saturation, and Δt = time increment (0.25 × 10 −12 s) [16][17][18][19]. Storage media used to record one bit information consisted of parallel-pipes, called nano-dots, with lateral dimension of 50 × 50 nm 2 in yz direction and a thickness of < 100 nm in x direction to design a ultra-thin strong perpendicular magnetic anisotropy media that allows data record up to hundreds of Gb/in 2 .…”