Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 20: Transport: Spincaloric Transport (jointly with MA)

TT 20.2: Talk

Monday, March 11, 2013, 15:15–15:30, H22

Tunnel magneto-Seebeck effect in high temperature gradients — •Marvin Walter¹, J. C. Leutenantsmeyer¹, V. Zbarsky¹, T. Eggebrecht¹, M. Münzenberg¹, K. Rott², A. Böhnke², G. Reiss², A. Thomas², M. Czerner³, and C. Heiliger³ — ¹I. Phys. Inst., Universität Göttingen, Germany — ²Dept. of Physics, Bielefeld University, Germany — ³I. Phys. Inst., Universität Giessen, Germany

CoFeB/MgO/CoFeB devices showing a giant TMR effect are possible candidates for the generation of spin-currents by thermal heating and the tunnel magneto-Seebeck effect was already observed. It is theoretically predicted that for a 3 monolayer MgO barrier the torque of the spin-polarized tunneling electrons might be sufficient to observe thermal spin transfer torque (T-STT).

The samples presented in this work consist of a minimal pseudo-spin-valve stack with sputtered Ta and CoFeB layers and an e-beam evaporated MgO barrier with thicknesses down to 3 monolayers. The MTJs are heated by a Ti:Sa femtosecond laser to achieve high temperature gradients. The heating of the MTJ by a femtosecond laser is simulated using finite element methods. Using the parameters observed in the experimental setup, the simulations show temperature differences across the MgO barrier of more than 10K for a duration in the order of picoseconds. This temperature difference should be sufficient to achieve T-STT. Furthermore, the thermomagnetoelectric properties in high temperature gradients of MTJs with perpendicular magnetic anisotropy and switching current densities of 2· 10⁵ A/cm² are investigated.