We have studied the spin torque efficiency of Pt_1−xBi_x/Co based heterostructures for spin–orbit torque (SOT) switching devices. While the field-like component of the SOT shows a relatively small change with the Bi concentration (x), the damping-like component (ξ_DL) abruptly increases with increasing x. The increase in ξ_DL with x is largely associated with the change in the Pt_1−xBi_x layer resistivity (ρ_xx). The spin Hall conductivity (σ_SH) estimated from ξ_DL and ρ_xx remains nearly constant at ∼830 (ℏ/e) Ω⁻¹ cm⁻¹ for 0 < x ≲ 0.6. Further substitution of Bi results in the formation of PtBi₂, which causes smaller σ_SH than that of alloys with smaller x. The magnetic easy axis of a 0.6 nm thick Co layer points along the film normal when x is smaller than ∼0.7. Exploiting these characteristics, we show current-induced magnetization switching in the heterostructures. The efficiency to switch a perpendicularly magnetized Co layer is the largest when x ∼ 0.5. These results demonstrate the potential of Pt_1−xBi_x alloys for spin–orbit torque magnetization switching devices.

中文翻译：

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Pt1-xBixalloys 中的电荷-自旋转换用于自旋-轨道扭矩切换

我们已经研究了用于自旋轨道扭矩 (SOT) 开关器件的 Pt _{1- x} Bi _x /Co 基异质结构的自旋扭矩效率。虽然 SOT 的类场分量随 Bi 浓度 ( x ) 的变化相对较小，但类阻尼分量 ( ξ _DL ) 会随着x 的增加而突然增加。ξ _DL随x的增加很大程度上与 Pt _{1- x} Bi _x层电阻率 ( ρ _xx ) 的变化有关。从ξ估计的自旋霍尔电导率 ( σ _SH )对于 0 < x ≲ 0.6，_DL和ρ _xx在 ∼830 ( ℏ / e ) Ω ^-1  cm ^-1处几乎保持不变。Bi 的进一步取代导致 PtBi ₂的形成，这导致σ _SH小于具有较小x的合金的σ _SH。当x小于 ~0.7时，0.6 nm 厚的 Co 层的易磁化轴指向薄膜法线。利用这些特性，我们展示了异质结构中电流感应的磁化转换。当x时，切换垂直磁化 Co 层的效率最大～ 0.5。这些结果证明了 Pt _{1- x} Bi _x合金用于自旋轨道扭矩磁化开关器件的潜力。