Thermal gradients and anomalous Nernst effects in membrane-supported nonlocal spin valves
Thermal gradients and anomalous Nernst effects in membrane-supported nonlocal spin valves
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DOI：
10.1103/physrevb.100.104404
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发表时间：
2019-09
影响因子：
3.7
通讯作者：
R. Bennet;A. Hojem-;B. Zink
中科院分区：
文献类型：
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作者：
R. Bennet;A. Hojem-;B. Zink
金属非局域自旋阀(NLSVs)在现代自旋电子学中非常重要，因为它们能够分离纯自旋电流和电荷电流。这些金属纳米结构通常由宽度在深亚微米范围内的特征构成，在运行中产生显著的温度梯度，产生的热量对自旋注入和输运具有重要影响。为了显著降低衬底的热导，我们利用电子束纳米光刻技术在500 nm氮化硅(Si-N)薄膜上制备了具有Ni-Fe合金铁磁纳米线和铝自旋沟道的非负反馈薄膜。虽然自旋电子系统中的热工程的这个极端例子以基于早期工作的预期方式增加了背景非局部信号，但它也增强了热电效应，包括反常能斯特效应，并揭示了一种以前未知的热辅助自旋注入，其结果是纯粹的面内热梯度。我们研究了这些效应作为温度的函数，并通过与计算单一温度下的温度梯度的二维有限元模型的仔细比较，证明了35 nm厚的Ni-Fe合金在T=200K时的反常能斯特系数RN=0.17，与以前对薄膜的这种效应的少数测量结果一致。
Metallic non-local spin valves (NLSVs) are important in modern spintronics due to their ability to separate pure spin current from charge current. These metallic nanostructures, often constructed from features with widths in the deep sub-micron regime, generate significant thermal gradients in operation, and the heat generated has important consequences for spin injection and transport. We use e-beam nanolithography to manufacture NLSVs with Ni-Fe alloy ferromagnetic nanowires and aluminum spin channels on 500 nm silicon nitride (Si-N) membranes in order to lower the thermal conductance of the substrate dramatically. While this extreme example of thermal engineering in a spintronic system increases the background non-local signals in ways expected based on earlier work, it also enhances thermoelectric effects, including the anomalous Nernst effect and reveals a previously unknown thermally-assisted electrical spin injection that results from a purely in-plane thermal gradient. We examine these effects as a function of temperature and, by careful comparison with 2D finite element models of the thermal gradients calculated at a single temperature, demonstrate that the anomalous Nernst coefficient of the 35 nm thick Ni-Fe alloy, RN = 0.17 at T = 200 K, is in line with the few previous measurements of this effect for thin films.