Shape anisotropy effect on magnetization reversal induced by linear down chirp pulse

Abstract

We investigate the shape anisotropy effect on the magnetization reversal of a nanoparticle driven by a down-chirp microwave field pulse (DCMP). Based on the Landau–Lifshitz–Gilbert equation, numerical results reveal that the microwave amplitude, initial frequency, and chirp rate of DCMP decrease with the increase of shape anisotropy. For a certain shape of the nanoparticle, the reversal time is significantly reduced. These findings can be attributed as the shape anisotropy opposes the magnetocrystalline anisotropy, and thus the energy barrier decreases. The result of damping dependence of reversal indicates that there exists an optimal damping situation at which magnetization is fastest. Moreover, the required microwave field amplitude can be lowered by applying the spin-polarized current simultaneously. The usage of an optimum combination of DCMP and current is suggested to achieve cost-effective and faster switching. So these findings might be useful to realize the fast and power-efficient data storage device.