Influence Of A Composite Free Layer Structure On Thermal Stability Of Perpendicular Magnetic Tunnel Junction

Perpendicular magnetic tunnel junctions (pMTJs) with a CoFeB/W/CoFeB/MgO composite free layer are experimentally investigated. Magnetic anisotropy and tunneling magnetoresistance (TMR) are determined as functions of ferromagnetic (CoFeB) and capping (MgO) layer thicknesses using the ferromagnetic resonance technique. In pMTJs fabricated into 130 and 150-nm diameters, the TMR ratio > 160% and the thermal stability factor Delta > 60 are measured for the MgO capping layer thickness of t(MgO) >= 1 nm. The voltage vs. magnetic field stability diagram indicates field-free current induced switching with voltages vertical bar V-S vertical bar < 0: 5V. Published by AIP Publishing.