Inherent spin transfer torque driven switching current fluctuations in magnetic element with in-plane magnetization and comparison to perpendicular design

摘要

This paper presents a systematic micromagnetic modeling study on switching current fluctuations in both in-plane and perpendicular spin-transfer-torque (STT) magnetoresistive random access memory devices. For the magnetic tunnel junction (MTJ) with in-plane magnetization, high-order spin wave modes are excited during a STT-driven switching, which leads to an inherently broad switching current distribution. If the MTJ size is not sufficiently small, a stable vortex can be formed over a wide range of current amplitudes. In contrast, the excitation of such high-order spin waves is absent in STT switching of MTJs with perpendicular magnetic anisotropy. Consequently, the fluctuation in switching current amplitude or pulse duration is significantly smaller in comparison.