Boehnke Alexander, Walter Marvin, Roschewsky Niklas, Eggebrecht Tim, Drewello Volker, Rott Karsten, Münzenberg Markus, Thomas Andy, Reiss Günter
Thin Films and Physics of Nanostructures, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany.
Rev Sci Instrum. 2013 Jun;84(6):063905. doi: 10.1063/1.4811130.
Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the μs time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects.
最近，几个研究小组报道了磁隧道结中的自旋相关热电效应。在本文中，我们展示了一种用于对单个微米到纳米尺度隧道结的热电压和热电流进行时间分辨测量的装置。使用电调制二极管激光器在隧道结层堆叠上产生温度梯度。这种激光调制技术能够记录时间相关的热电压信号，其时间分辨率仅受热电压前置放大器的限制。到目前为止，时间相关的热电压还无法得到解释。现在，利用本文展示的装置，有可能在微秒时间范围内区分不同塞贝克电压对整体测量电压信号的贡献。开发了一个模型电路来解释不同样品类型上的这些电压贡献。此外，还将表明，只有当激光光斑直接位于磁隧道结顶部中心时，才能观察到由磁隧道结产生的电压信号，这使得能够从横向区分这些效应。
