Seebeck effect in magnetic tunnel junctions
Seebeck effect in magnetic tunnel junctions
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DOI：
10.1038/nmat3076
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发表时间：
2011-10-01
期刊：
影响因子：
41.2
通讯作者：
Heiliger, Christian
中科院分区：
文献类型：
--
作者：
Walter, Marvin;Walowski, Jakob;Heiliger, Christian
在磁性纳米结构中产生温度梯度导致了一个新的研究方向，即磁效应和热电效应的结合(1-5)。在这里，我们演示了这一类中的一个重要效应的观测：磁塞贝克效应。当磁组态改变基于电荷的塞贝克系数时，可以观察到这一现象。特别地，在隧道结中，塞贝克系数在从平行磁性构型向反平行磁性构型转变的过程中发生变化。在这一点上，它类似于隧道磁阻。平行和反平行组态的Seebeck系数与电荷-Seebeck效应中已知的电压量级相同。效应的大小和符号可以由邻近势垒的电极原子层的组成和温度来控制。电子态密度相对于费米能级的几何中心决定了塞贝克效应的大小。在实验上，我们实现了8.8%的磁塞贝克效应，这是由于从反平行到平行方向的电压变化约为-8.7mU Vk-1，接近于预测值-12.1 mU Vk-1。与自旋-塞贝克效应不同的是，它可以直接测量为电压变化，而不需要转换自旋电流。
Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects(1-5). Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about -8.7 mu VK-1 from the antiparallel to the parallel direction close to the predicted value of -12.1 mu VK-1. In contrast to the spin-Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current.