Figure 1: Schematic of the experiment.

(a) The studied MTJ consists of a bottom reference layer Ta(5 nm)/PtMn(25 nm)/Co₉₀Fe₁₀(2 nm)/Ru(0.8 nm)/Co₉₀Fe₁₀(3 nm) and a free layer Co₉₀Fe₁₀(2 nm)/Ni₈₀Fe₂₀(5 nm)/Ru(4.8 nm)/Au(10 nm) separated by an Al₂O₃ barrier. To generate a temperature difference between both sides of the Al₂O₃ barrier, one electrode lead was heated using the laser beam from a laser diode with the wavelength of 780 nm at a maximum power of 125 mW. The open-circuit voltage was measured by the nanovoltmeter at room temperature (RT) with an applied magnetic field μ₀H up to 0.3 T along the in-plane easy axis. (b) In the presence of the temperature difference ΔT in the MTJ, the generated thermovoltage ΔV depends on the relative magnetization alignment of the two ferromagnetic layers. (c) The thermotunnel current I was measured by the system sourcemeter connecting the MTJ in a closed circuit without applied voltage.