Experiments on giant thermal magnetogalvanic efects in magnetic tunnel junctions

磁隧道结巨热磁电效应实验

• 批准号: 198020709
• 负责人: Professor Dr. Markus Münzenberg
• 金额: --
• 依托单位: Institut für Metallische Werkstoffe
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/198020709?language=en
• 关键词: Experiments; giant; thermal; magnetogalvanic; efects

Spin-dependent Seebeck effects have been discovered in lateral devices and giant-magnetoresistance (GMR) nanopillar junctions. Thermally driven spin accumulation leads to a magnetothermopower over length on the scale of the spin diffusion. Spin-wave excitations also contribute to thermally driven magnetothermopower over length on the order of millimeters. We will focus on giant-tunneling-magnetoresistance (TMR) devices (Heusler/MgO/Heusler and Co-Fe-B/MgO/Co-Fe-B) with high TMR values of >200%. First, the strong spin asymmetry of the thermal tunneling current leads to a spin-dependent shift of the chemical potential. In joint collaboration with a theory project, high magnetothermopowers (MTEPs) of ~60 μV have been predicted to and show peculiar temperature dependence. Second, inelastic tunneling processes may open tunneling channels in half-metallic junctions, mirroring the different magnon temperatures on both side of the tunnel barrier. To determine the spin-dependent Seebeck coefficients in giant tunneling magnetoresistance (TMR) devices, we will develop techniques to generate temperature gradients in tunnel junctions by resistive and optical heating. In addition, we will lay the foundation to perform not only static heating, which allows only very small temperature gradients of a one tenth of a degree temperature drop at the tunnel barrier, but also dynamic experiments with nanosecond electrical pulses and femtosecond optical excitation. Our aim is to understand, in close collaboration with our theoretical collaborator, the origin of high spin-dependent Seebeck coefficients arising from strong spin asymmetries of the tunneling probability in giant tunneling magnetoresistance devices.

在横向器件和巨磁电阻(GMR)纳米结中已经发现了自旋相关的Seebeck效应。热驱动的自旋积累导致了自旋扩散尺度上的磁热电势。自旋波的激发也对长度为毫米量级的热驱动的磁热功率有贡献。我们将重点研究巨隧穿磁阻(TMR)器件(Heusler/MgO/Heusler和Co-Fe-B/MgO/Co-Fe-B)，其TMR值高达&gt；200%。首先，热隧穿电流的强自旋不对称性导致了化学势的自旋相关位移。在与一个理论项目的合作下，预测了约60μV的高磁热电偶(MTEP)，并显示出特殊的温度依赖性。第二，非弹性隧穿过程可能打开半金属结中的隧穿通道，反映了隧道势垒两侧不同的磁振子温度。为了确定巨隧穿磁阻(TMR)器件中与自旋相关的Seebeck系数，我们将开发通过电阻和光加热在隧道结中产生温度梯度的技术。此外，我们将为不仅进行静态加热(只允许隧道势垒温降十分之一度的非常小的温度梯度)，而且还将使用纳秒电脉冲和飞秒光激励进行动态实验奠定基础。我们的目标是与我们的理论合作者密切合作，了解巨隧穿磁阻器件中隧道几率的强自旋不对称性所产生的高自旋相关塞贝克系数的来源。