Electroforming, magnetic and resistive switching in MgO-based tunnel junctions

Magnetic tunnel junctions (MTJs) are under investigation since they offer great potential for applications in magnetic memories. An interesting effect in TJs concerns non-volatile resistive switching of non-magnetic origin. We report magnetic (magnetoresistance) and structural (resistive; R) switching in MgO-based MTJs (barrier thicknesses t = 0.75, 1.35 nm). As-grown MTJs display R-switching only in the thinnest series, while thicker barrier samples need an electroforming step for R-switching to occur. Forming changes the electrical resistance temperature dependence, from tunnel- to metallic-like, revealing the formation of conductive bridges across the barrier which, leading to local high electrical fields and temperatures, are essential for resistive switching.