Experimental setup for measurements of the TMS effect: (a) Optical setup with confocal microscope including a fast photodiode (PD) and a CCD camera, (b) electrical setup showing the connections of the sample and optoelectronic components to the lock-in amplifier and oscilloscope.
Low laser power and different substrates: TMR (blue circles, left scale) and TMS (red line, right scale) of nominally identical MTJs on (a) Si/SiO2 and (b) MgO substrates obtained with a laser power of 10 mW and 15 mW, respectively. The arrows represent the relative orientation of the magnetic layers. The TMR and TMS values are given in Table II .
High laser power: Seebeck voltage (a) and Seebeck current (b) measured at a laser power of 150 mW.
Time-dependent voltage signals of MTJs on (a) Si/SiO2 and (b) MgO substrate with a laser power of 10 mW and 15 mW, respectively. As blue circles Simulation Program with Integrated Circuit Emphasis (SPICE) simulations are shown, as described in Sec. V .
Model circuit for MTJs on (a) insulating MgO and (b) capacitively coupled p-type Si substrates. (c) Inside the samples on Si two heat gradients ΔT MTJ and ΔT Si produce thermovoltages V MTJ and V Si, respectively. When the laser is positioned on the MTJ (red) the effective temperature gradient ΔT eff between the contact points x 1 and x 2 is larger compared to the laser positioned between the MTJ and the edge of the sample (blue).
(a) Short distances: Measurements in the vicinity of the MTJ; the positions are shown in the inset. Laser spot and MTJ are located at P1, the heated area is sketched in red. (b) Large distances: Measurements of a different MTJ at distances more than factor of 10 larger as in the case of (a).
Material parameters for COMSOL simulations. If not specified otherwise, the values are taken from Refs. 10 and 26–28 . The thermal conductivities used in the simulations are printed in bold letters. Experimental thin film values are given where available.
Comparison of TMR and TMS on MgO and Si/SiO2 samples.
Basic estimations for calculating the resistance and capacitance in the model circuit for simulations.
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