Spin-orbit torque (SOT) offers ultrafast magnetic switching in the subnanosecond regime for magnetoresistive random-access memory (MRAM) as an alternative to future cache memories. However, one main obstacle to the development of perpendicular SOT-MRAM is that a small in-plane external field is required to achieve deterministic magnetization switching. Here we eliminate the external magnetic field for deterministic SOT switching by utilizing the stray field in a magnetic tunnel junction (MTJ) structure. The MTJ consists of a perpendicularly magnetized CoFeB free layer and an in-plane magnetized reference layer that provides a stray field. Unlike usual SOT switching in a single ferromagnet, four switching phases as well as unique critical switching current dependence on the applied in-plane magnetic fields have been observed. This letter demonstrates the effectiveness of stray-field assisted field-free SOT switching in MTJ structures that may extend to eliminate the main obstacle of SOT-MRAM in practical applications.

中文翻译：

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杂散磁场的磁性隧道结结构中的无场自旋轨道转矩切换

自旋轨道转矩（SOT）在亚纳秒范围内为磁阻随机存取存储器（MRAM）提供了超快的磁性切换，可以替代未来的高速缓存。但是，发展垂直SOT-MRAM的一个主要障碍是需要小的平面内外部磁场来实现确定性的磁化切换。在这里，我们通过利用磁性隧道结（MTJ）结构中的杂散场来消除用于确定性SOT切换的外部磁场。MTJ由垂直磁化的CoFeB自由层和提供杂散场的面内磁化参考层组成。与单个铁磁体中的常规SOT开关不同，已经观察到四个开关相位以及对所施加的面内磁场的独特的临界开关电流依赖性。