Thermal effect on microwave pulse-driven magnetization switching of Stoner particle

Abstract

We investigate the cosine-chirped microwave pulse (cosine CMP)-driven magnetization switching of a nanoparticle or stoner particle at a finite temperature in the framework of the stochastic Landau–Lifshitz-Gilbert equation. Numerical results reveal that the ultrafast and efficient magnetization switching is robust even at room temperature, and hence we estimate the maximal temperature at which the magnetization switching is still valid. The maximal temperature increases with the enlargement (by increasing cross-sectional area) of the nanoparticle/stoner particle volume to a certain value, and afterward, the maximal temperature decreases with the further increment of the nanoparticle size. Initially, the shape anisotropy (approximated by the easy-plane) coefficient does not become dominant although the stoner particle volume increases, which plays a role in increasing thermal stability (maximal temperature), and later the shape anisotropy field becomes dominant, which opposes the uniaxial anisotropy, i.e., reduces the energy barrier, which reduces the maximal temperature. For smaller volumes, the parameters of cosine CMP show a decreasing trend with temperature. The initial frequency requirement significantly decreases with shape anisotropy. Therefore, these findings might be useful to realize cosine CMP-driven fast and energy-efficient magnetization switching in device applications.

Magnetization reversal of ferromagnetic nanosample by circularly polarized radiation pulse under resonance condition

“…This is a classical problem and the correct incorporation of, e.g., anisotropy energy into the quantum Hamiltonian is hardly a trivial task (see, for instance, [30]). Some experiments [31,32] show fast and robust magnetization reversal under circularly polarized radiation. At the same time, theoretical analysis in the framework of the Landau-Lifshitz-Gilbert equation admits complicated behavior, including bifurcations and multiperiodic orbits [33].…”