Negative spin Hall angle and large spin-charge conversion in thermally evaporated chromium thin films
Negative spin Hall angle and large spin-charge conversion in thermally evaporated chromium thin films
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DOI：
10.1063/5.0085352
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发表时间：
2022-03
影响因子：
3.2
通讯作者：
S. Bleser;R. Greening;M. Roos;L. Hernandez;X. Fan;B. Zink
中科院分区：
文献类型：
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作者：
S. Bleser;R. Greening;M. Roos;L. Hernandez;X. Fan;B. Zink
自旋到电荷的转换和反向过程现在是自旋电子学广泛的基础和应用研究中至关重要的物理过程。在这里，我们实验证明了利用纵向自旋塞贝克效应（LSSE）在热蒸发铬薄膜中有效的自旋到电荷转换。我们展示了在室温下沉积在大块多晶钇铁石榴石（YIG）衬底上的厚度从2到11纳米的Cr薄膜的LSSE结果。在匹配的YIG衬底上生长相同标称厚度的Cr和溅射Pt薄膜，对比测量到的LSSE电压[公式：见文]表明，两种薄膜都表现出相当大的自旋-电荷转换。如前所述，对于其他形式的Cr，蒸发Cr/YIG的LSSE信号显示与Pt相反的符号，表明Cr具有负的自旋霍尔角，[公式：见文本]。我们也给出了在YIG上同样蒸发的Cr膜的电荷电阻率的测量结果[公式：见原文]。与Pt相比，这些值很大，并且在相同的厚度下与[公式：见文本]-W相当。[公式：见文]和[公式：见文]随薄膜厚度的非单调行为表明，蒸发Cr中自旋到电荷的转换可以通过Cr中的自旋密度波反铁磁性来改变，我们期望其具有与先前研究的溅射膜不同的应变状态。
Spin-to-charge conversion and the reverse process are now critically important physical processes for a wide range of fundamental and applied studies in spintronics. Here, we experimentally demonstrate effective spin-to-charge conversion in thermally evaporated chromium thin films using the longitudinal spin Seebeck effect (LSSE). We present LSSE results measured near room temperature for Cr films with thicknesses from 2 to 11 nm, deposited at room temperature on bulk polycrystalline yttrium-iron-garnet (YIG) substrates. Comparison of the measured LSSE voltage, [Formula: see text], in Cr to a sputtered Pt film at the same nominal thickness grown on a matched YIG substrate shows that both films show comparably large spin-to-charge conversion. As previously shown for other forms of Cr, the LSSE signal for evaporated Cr/YIG shows the opposite sign compared to Pt, indicating that Cr has a negative spin Hall angle, [Formula: see text]. We also present measured charge resistivity, [Formula: see text], of the same evaporated Cr films on YIG. These values are large compared to Pt and comparable to [Formula: see text]-W at a similar thickness. Non-monotonic behavior of both [Formula: see text] and [Formula: see text] with film thickness suggests that spin-to-charge conversion in evaporated Cr, which we expect has a different strain state than previously investigated sputtered films, could be modified by spin density wave antiferromagnetism in Cr.