Switching characteristics of MgO-based MTJ with intermediate state

The resistance change of magnetic tunnel junctions (MTJs) is used to store digital information in spin-transfer-torque magnetoresistive random-access memory. In some MTJs, intermediate (IM) states occur between two stable resistance states just after the application of a switching pulse. In this study, the effect of IM states on switching is investigated. IM states increase the switching voltage, and their probability is significantly high at a narrow pulse width. For no-error switching, MTJs with IM states require higher voltages and wider pulse widths compared with MTJs without IM states. A 300 nm MTJ has multiple IM states, whereas a 120 nm MTJ has only one IM state. Overall, a large MTJ’s free layer has multiple regions with different switching characteristics, and switching occurs stepwise through IM states.