Temperature dependence of magnetoresistance and surface magnetization in ferromagnetic tunnel junctions

The temperature dependence of spin-polarized tunneling is investigated between 77 and 420 K for various ferromagnetic tunnel junctions. Both the junction resistance and the magnetoresistance decrease with increasing temperature $T.$ The experimental results are successfully described by a model that includes two current contributions. The dominant one is elastic, spin-polarized tunneling between the two ferromagnetic electrodes, each with an electron polarization P that decreases with T due to thermally excited spin waves according to P∝(1-αT3/2), i.e., in the same way as the surface magnetization. A smaller second conductance is due to assisted, spin-independent tunneling which we find to be proportional to T^1.35±0.15.