Tunneling hot spots and heating in magnetic tunnel junctions

In this work the thermal heating of tunnel junctions is investigated doing one-dimensional numerical simulations by solving the heat equation. The temperature increase is proportional to the power density jV, which is confirmed by transport measurements on patterned μm size junctions. The observed temperature increase was 2.3 K/(mW μm−2) compared to a simulation result of 0.9 K/(mW μm−2). Tunneling AFM measurements on 4, 5.4, and 6.7 Å barrier half-junctions, show hot spots with current densities up to 13 times the average density value. The current concentration could explain the higher heating observed experimentally compared to the simulated value. The hot spot density is 600–900/μm2 occupying roughly 5% of the barrier surface.