Properties of CoPt ferromagnetic layers for application in spin light-emitting diodes

The magnetic properties of Co$_{45}$Pt$_{55}$ films deposited by electron-beam evaporation in vacuum have been studied. The measurements of the Faraday and Kerr magnetooptical effects confirm the presence of the easy-magnetization axis perpendicular to the Co$_{45}$Pt$_{55}$ surface. It is shown that the perpendicular magnetic anisotropy and the residual magnetization are retained at 300 K for a long time. The magnetic characteristics of the Co$_{45}$Pt$_{55}$ layer surface have been studied by magnetic force microscopy, and “circular” mobile magnetic structures have been detected. The spin light-emitting diodes based on In(Ga)As/GaAs heteronanostructures with Co$_{45}$Pt$_{55}$ contact layers were fabricated. These diodes emit circularly-polarized light in the absence of an external magnetic field.