Origin of temperature dependence in tunneling magnetoresistance

We present detailed measurements of the differential resistance ($\upd V/\upd I$) of state-of-the-art $\chem{FM/AlO}$x/$\chem{FM}$ magnetic tunnel junctions (MTJ) as a function of applied bias and temperature. Temperature effects are particularly significant in physical quantities involving narrow features such as those at low-voltage bias. We show that the temperature evolution of the tunneling characteristics and, in particular, the pronounced rounding of the $\upd V/\upd I$ curves with increasing temperature can be well explained by thermal smearing of the tunneling electron energy distribution