Spin- and Magneto-Seebeck effects in novel magnetic thin film materials

最近在铁磁金属中发现了自旋相关的Seebeck系数（SSE），立即引发了大量的研究活动。这种效应现在也在磁性半导体中被观察到。令人惊讶的是，也绝缘铁磁体覆盖的Pt条产生相应的信号中的反自旋霍尔效应（ISHE），这是用来观察SSE。特别是后一种观察需要在绝缘体（在这种情况下为LaY2Fe5O12）和金属（Pt）之间引入热激活界面自旋交换。 我们建议调查SSE的比较四种类型的样品：经典的铁磁体与已知的自旋极化，高度自旋极化的Heusler合金，这是接近的相变从铁磁金属顺磁半导体和REYZ Heusler化合物（RE：稀土，Y=Au，Pt），这是拓扑绝缘体，由于它们的带反转。对于选定的样品，我们建议在铁磁体和检测金属之间另外引入薄的间隔层：隧道势垒或4f金属，如Tb。将制备相应的薄膜器械，并使用带有Pt或Pd覆盖条的ISHE表征样品特性。现有的设备将被扩展，使也能够测量的SSE的温度依赖性。从这些实验中，我们期望首先有助于理解的影响，带结构的上证所。其次，我们希望获得有关铁磁体和探测器金属之间的界面的影响的实验数据。隧穿势垒应充当去耦间隔物，并且预期ISHE信号随着势垒厚度的增加而衰减。4f金属应该反铁磁耦合到下面的铁磁体，因此ISHE的符号反转应该发生，再次具有一定但未知的衰减长度。

The recent discovery of a Spin Dependent Seebeck Coefficient (SSE) in ferromagnetic metals has immediately initiated large research activities. The effect now has been also observed in magnetic semiconductors. Surprisingly, also insulating ferromagnets covered by a Pt-stripe produced corresponding signals in the Inverse Spin Hall Effect (ISHE) which is used to observe the SSE. In particular the latter observation required to introduce a thermally activated interface spin exchange between the insulator (LaY2Fe5O12 in this case) and the metal (Pt). We propose to investigate the SSE by a comparison of four types of samples: Classical ferromagnets with known spin polarization, highly spin polarized Heusler alloys which are close to a phase transition from ferromagnetic metal to paramagnetic semiconductor and REYZ Heusler compounds (RE: Rare Earth, Y=Au, Pt) which are topological insulators due to their band inversion. For selected samples, we propose to additionally introduce thin spacer layers between the ferromagnet and the detecting metal: a tunnel barrier or a 4f-metal such as Tb. The corresponding thin film devices will be prepared and the ISHE with a Pt or a Pd cover stripe will be used to characterize the sample properties. The existing apparatus will be extended to enable also measurements of the temperature dependence of the SSE. From these experiments, we expect first a contribution to the understanding of the influence of the band structure on the SSE. Second, we hope to gain experimental data about the influence of the interfaces between the ferromagnet and the detector metal. The tunneling barriers should act as decoupling spacers and a decay of the ISHE signal with increasing barrier thickness is expected. The 4f-metal should couple antiferromagnetically to the underlying ferromagnet and thus a sign reversal of the ISHE should occur, again with a certain but yet unknown attenuation length.