Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 38: Magnetocaloric Effects (joint session MA/TT)

TT 38.8: Talk

Tuesday, March 13, 2018, 11:30–11:45, EB 407

Exploring three-dimensional temperature gradients in magnetic tunnel junctions: Anomalous Nernst effect — Ulrike Martens¹, Torsten Huebner², Henning Ulrichs³, Oliver Reimer², Timo Kuschel², Ronnie Tamming⁴, Chia-Lin Chang⁴, Raanan Tobey⁴, Andy Thomas⁵, Markus Münzenberg¹, and •Jakob Walowski¹ — ¹Universität Greifswald, Greifswald, Germany — ²Bielefeld University, Bielefeld, Germany — ³Universität Göttingen, Göttingen, Germany — ⁴University of Groningen, Groningen, The Netherlands — ⁵IFW Dresden, Institute for Metallic Materials, Dresden, Germany

We measure the anomalous Nernst effect (ANE) generated on a nanometer length scale by micrometer sized temperature gradients in magnetic tunnel junctions (MTJs). The ANE is extracted by analyzing the influence of in-plane temperature gradients on the tunnel magneto-Seebeck effect (TMS) in in-plane magnetized MTJs based on CoFeB electrodes with uniaxial magnetic anisotropy and an MgO tunnel barrier. The direction controlled temperature gradients are created by a focused laser spot. The spatial extent of the measured effects is defined by the MTJ size, while the spatial resolution is given by the laser spot size and the step size of its lateral translation. The measurement method is highly sensitive to low voltages and yields an ANE coefficient of K_N≈1.6· 10⁻⁸ V/TK for CoFeB. At such sensitivity, the generated ANE effect allows to expand the MTJs’ functionality from simple memory storage to nonvolatile logic devices and opens new application fields e.g. direction dependent temperature sensing.