Design of spin-injection-layer in all-in-plane spin-torque-oscillator for microwave assisted magnetic recording
Design of spin-injection-layer in all-in-plane spin-torque-oscillator for microwave assisted magnetic recording
复制标题
微波辅助磁记录全平面自旋扭矩振荡器自旋注入层设计
DOI：
10.1016/j.jmmm.2018.12.081
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发表时间：
2019
影响因子：
2.7
通讯作者：
K.Hono
中科院分区：
文献类型：
--
作者：
H.Sepehri-Amin;W.Zhou;S.Bosu;C.Abert;Y.Sakuraba;S.Kasai;D.Suess;K.Hono
介绍了一种用于微波辅助磁记录（MAMR）的新型自旋力矩振荡器（STO）--全面内STO，它由自旋注入层（SIL）和场产生层（FGL）组成，由于形状各向异性，场产生层具有有效的面内易磁化轴。在该器件中，电子从SIL注入到FGL，同时SIL和FGL的磁化被1.0T的外部磁场饱和到面外。微磁学模拟表明，利用自旋转移矩可以将SIL的磁化方向切换到与外加磁场相反的方向。这导致FGL中更大的自旋积累和在低偏置电流密度下具有大锥角的振荡。我们设计SIL以降低SIL磁化切换所需的临界电流密度Jc。在SIL中具有较小饱和磁化强度的材料降低Jc。SIL的自旋极化越小，SIL中的自旋积累越大，方向与磁化方向相反，导致Jc减小。这使得SIL的磁化切换在小J c下，随后FGL以高于20 GHz的频率振荡，具有45-50°的大面外振荡锥角。实验上用两种SIL材料Co2 Fe（Al0.5Si0.5）Heusler合金和Fe 67 Co 33研制了STO，前者具有B2晶体结构，自旋极化大，后者具有A2晶体结构，自旋极化小。基于场相关电阻变化实验研究了直径为1.60 nm的STO中SIL和FGL的磁化结构，并基于微磁学模拟讨论了其振荡行为.
A new type of spin-torque-oscillator (STO), all-in-plane STO, is introduced for microwave assisted magnetic recording (MAMR) that consist of a spin-injection-layer (SIL) and a field-generating-layer (FGL) with an effective in-plane easy axis due to the shape anisotropy separated with a metallic spacer. In this device, electrons are injected from SIL to FGL while the magnetization of the SIL and FGL is saturated to the out-of-plane by the external magnetic field of ∼1.0 T. Micromagnetic simulations showed that the magnetization direction of SIL can be switched to the opposite direction to that of the applied external magnetic field by the use of spin-transfer-torque. This results in a larger spin accumulation in FGL and its oscillation with a large cone angle at a low bias current density. We designed SIL to reduce the critical current density,Jc, required for the magnetization switching of SIL. Materials with a smaller saturation magnetization in SIL reduceJc. Smaller spin polarization of SIL leads to a larger spin accumulation in SIL with an opposite direction to the magnetization, resulting in a reduction ofJc. This enables magnetization switching of SIL in smallJcfollowed by oscillation of FGL with frequency above 20 GHz with a large out-of-plane oscillation cone angle of 45–50°. The validity of this finding was studied experimentally by developing STO with two SIL materials, Co2Fe(Al0.5Si0.5) Heusler alloy and Fe67Co33, the former has the B2 crystal structure with a large spin polarization and the latter has the A2 crystal structure with a smaller spin polarization. The magnetization configuration of SIL and FGL in STO with a diameter of ∼60 nm is investigated experimentally based on the field dependent resistance change and the oscillation behavior is discussed based on the micromagnetic simulations.