Vortex spin-torque oscillator using Co2FexMn1-xSi Heusler alloys
Vortex spin-torque oscillator using Co2FexMn1-xSi Heusler alloys
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DOI：
10.1103/physrevb.94.094419
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发表时间：
2016-09-16
影响因子：
3.7
通讯作者：
Takanashi, Koki
中科院分区：
文献类型：
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作者：
Yamamoto, Tatsuya;Seki, Takeshi;Takanashi, Koki
我们利用外延生长的Co2FexMn1-xSi(CFMS)Heusler合金薄膜，研究了电流垂直于平面的巨磁电阻结中的自旋转移扭矩驱动的涡旋振荡。CFMS的软磁性和高自旋极化特性使我们能够以较低的阈值电流实现涡旋振荡，发射出大的微波功率。随着振荡阈值电流的降低，当Fe-Mn组成比一定时，输出功率最大，这与自旋-扭矩振荡的一般模型一致。通过与描述涡核平移运动的解析理论的比较，我们发现在本装置中激发的涡核运动沿厚度方向是不均匀的。尽管存在不均匀性，CFMS/间隔体界面区的回转半径仍接近实际铁磁层半径的75%，这表明CFMS基全金属结可用于实现大幅度的涡核运动。这一全面的研究也将有助于设计基于磁涡动力学的高性能全金属纳米振荡器。
We show spin-transfer-torque-driven vortex oscillations in current-perpendicular-to-plane giant magnetoresistance junctions using epitaxially grown Co2FexMn1-xSi (CFMS) Heusler alloy thin films. The soft magnetic property and high spin polarization of CFMS enable us to realize vortex oscillation emitting large microwave power with a low threshold current. The output power is maximized for a certain Fe-Mn composition ratio associated with a reduction of the threshold current for the oscillation, which is in agreement with a general model for spin-torque oscillation. Through comparison with an analytical theory that describes the translational motion of a vortex core, we show that the vortex core motion excited in the present device is inhomogeneous along the thickness direction. In spite of the inhomogeneity, the gyration radius at the CFMS/spacer interface region was estimated to be similar to 75% of the actual ferromagnetic layer radius, which indicates that the CFMS-based all-metallic junction is useful for achieving large-amplitude vortex core motion. This comprehensive investigation would also be useful for designing high-performance all-metallic nano-oscillators based on magnetic vortex dynamics.