Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

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

TT 38.12: Talk

Tuesday, March 13, 2018, 12:30–12:45, EB 407

Magneto-Seebeck Tunneling Across a Vacuum Barrier — •Cody Friesen and Stefan Krause — Department of Physics, University of Hamburg, Jungiusstr. 11A, 20355 Hamburg, Germany

The tunneling magneto-Seebeck (TMS) effect has been intensively studied both for its potential applications in e.g. waste heat recycling in electronics, and for the insights it can provide into fundamental solid state phenomena. This effect has been measured in planar junctions [1] and, as will be described in this talk, can also be measured using spin-polarized scanning tunneling microscopy (SP-STM).

The experiments were performed at low temperatures (T = 50 K) and in UHV conditions, on the Fe/W(110) multilayer system [2], using a laser-heated bulk Cr tip and active bias compensation. The non-collinear spin structures present in this sample system, and the atomic-scale lateral resolution of SP-STM, allowed for the imaging of a continuous range of relative tip-sample magnetization orientations.

Here, as in planar junctions, the measurement of the temperature gradient between electrodes is a significant challenge. We have estimated the tip-sample temperature difference using a linear thermal tip expansion model. To verify this, we have also directly predicted the Seebeck coefficient S using tunneling bias spectroscopy. We found these approaches to be in good agreement, suggesting a convenient spectroscopic approach to determining S on the atomic scale, even in the absence of a temperature gradient.

[1] M. Walter et al., Nat. Mater. 10, 10 (2011).

[2] S. Meckler et al., Phys. Rev. Lett. 103, 15 (2009).