Origin of temperature dependence in tunneling magnetoresistance

Abstract

Abstract. – We present detailed measurements of the differential resistance (dV/dI) of state-of-the-art FM/AlOx/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 dV/dI curves with increasing temperature can be well explained by thermal smearing of the tunneling electron energy distribution. Tunneling magnetoresistance [1] (TMR) in magnetic tunnel junctions (MTJ) continues to receive increasing attention [2], since high TMR values [3, 4] allow for applications such as magnetic random access memory [5] (MRAM) and magnetic read-heads [6]. Although the low-temperature TMR can reach the optimum values expected from Julliere’s model [1], even high-quality MTJs suffer a significant loss of TMR with increasing temperature. It was sug-gested that emission of surface magnons by tunneling electrons lead to extra current channels through the tunneling barrier. The contribution from these channels grows with the num-ber of thermally excited magnons, more so for the antiparallel (AP) configuration, with the