Microstructural and magnetic properties of CoFeZr films and the tunnel magnetoresistance behaviors of the magnetic tunnel junctions with amorphous CoFeZr ferromagnetic layers

Abstract

We investigated the composition dependence of the microstructure and magnetic properties of Co 90Fe 10–Zr film and the thermal and structural stability of MTJs with CoFeZr layers. As the Zr concentration in the Co 90Fe 10–Zr film increased, the grain size decreased rapidly, and the alloy films became a homogeneous amorphous phase when the concentration of Zr exceeded 15 at%. The TMR ratio of the MTJs with Co 90Fe 10 layers decreased when the samples were annealed at a temperature above 300 °C, whereas that of the MTJs with amorphous CoFeZr layers only started to decrease when they were annealed at a temperature above 350 °C. The MTJs with CoFeZr layers retained a significant TMR value of 28%, even after annealing at 450 °C. The enhanced structural quality of the interfaces improved the thermal stability of the MTJs with amorphous CoFeZr layers.