Energy efficient and fast reversal of a fixed skyrmions with spin current assisted by voltage controlled magnetic anisotropy

TL;DR

This paper demonstrates that voltage-controlled magnetic anisotropy enables energy-efficient, rapid reversal of fixed skyrmions with lower current than ferromagnetic reversal, promising for advanced magnetic memory devices.

Contribution

It introduces a method to reverse fixed skyrmions efficiently using voltage-controlled anisotropy, reducing current and time compared to traditional ferromagnetic switching.

Findings

Skyrmion reversal requires less current at low PMA levels.

Reversal of skyrmions is faster than ferromagnets under certain conditions.

Energy portraits confirm a different switching path at low PMA.

Abstract

Recent work [1,2] suggests that ferromagnetic reversal with spin transfer torque (STT) requires more current in a system in the presence of DMI than switching a typical ferromagnet of the same dimensions and perpendicular magnetic anisotropy (PMA). However, DMI promotes stabilization of skyrmions and we report that when the perpendicular anisotropy is modulated (reduced) for both the skyrmion and ferromagnet, it takes much smaller current to reverse the fixed skyrmion than to reverse the ferromagnet in the same time, or the skyrmion reverses much faster than the ferromagnet at similar levels of current. We show with rigorous micromagnetic simulations and energy portraits that the skyrmion switching proceeds along a different path at very low PMA which results in a significant reduction in the spin current required or time required for reversal. This can have potential for memory application where a relatively simple modification of the standard STT-RAM to include a heavy metal adjacent to the soft magnetic layer and with appropriate design of the tunnel barrier can lead to energy efficient and fast magnetic memory device based on the reversal of fixed skyrmions.