Wooten Brandi L, Vandaele Koen, Boona Stephen R, Heremans Joseph P
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA.
Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA.
Nanomaterials (Basel). 2020 Oct 21;10(10):2083. doi: 10.3390/nano10102083.
The spin-Seebeck effect (SSE) is an advective transport process traditionally studied in bilayers composed of a ferromagnet (FM) and a non-magnetic metal (NM) with strong spin-orbit coupling. In a temperature gradient, the flux of magnons in the FM transfers spin-angular momentum to electrons in the NM, which by the inverse spin-Hall effect generates an SSE voltage. In contrast, the Nernst effect is a bulk transport phenomenon in homogeneous NMs or FMs. These effects share the same geometry, and we show here that they can be added to each other in a new combination of FM/NM composites where synthesis via in-field annealing results in the FM material (MnBi) forming aligned needles inside an NM matrix with strong spin-orbit coupling (SOC) (Bi). Through examination of the materials' microstructural, magnetic, and transport properties, we searched for signs of enhanced transverse thermopower facilitated by an SSE contribution from MnBi adding to the Nernst effect in Bi. Our results indicate that these two signals are additive in samples with lower MnBi concentrations, suggesting a new way forward in the study of SSE composite materials.
自旋塞贝克效应（SSE）是一种传统上在由铁磁体（FM）和具有强自旋轨道耦合的非磁性金属（NM）组成的双层结构中研究的平流输运过程。在温度梯度下，FM中的磁振子通量将自旋角动量传递给NM中的电子，这些电子通过逆自旋霍尔效应产生SSE电压。相比之下，能斯特效应是均匀NM或FM中的体输运现象。这些效应具有相同的几何结构，我们在此表明，它们可以在一种新的FM/NM复合材料组合中相互叠加，其中通过场内退火合成会使FM材料（MnBi）在具有强自旋轨道耦合（SOC）的NM基体（Bi）内形成排列整齐的针状物。通过对材料的微观结构、磁性和输运性质进行研究，我们寻找了由MnBi对Bi中的能斯特效应的SSE贡献所促进的横向热功率增强的迹象。我们的结果表明，在较低MnBi浓度的样品中这两个信号是相加的，这为SSE复合材料的研究指明了一条新的道路。
