Degradation of magnetic tunnel junctions with thin AlOx barrier

The degradation of magnetic tunnel junctions (MTJs) with AlOx barrier was experimentally investigated. Constant voltage stress (CVS) measurement was carried out to monitor the time evolution of the conductance and tunneling magnetoresistance (TMR) of MTJs. The gradual increase of the stress-induced leakage current (SILC) was observed prior to the breakdown, following a power law function of stress time with an exponent of about 0.2-0.4, which is similar to the case of the ultrathin gate oxide films in MOSFETs. The measured TMR for SILC suggests that the spin-dependent current component would be involved in the early stage of degradation, while spin-independent conduction becomes dominant before the breakdown resulting in a decrease of TMR.