Evolution of in-plane magnetic anisotropy in sputtered FeTaN/TaN/FeTaN sandwich films

FeTaN/TaN/FeTaN sandwich films, FeTaN/TaN, and TaN/FeTaN bilayers were synthesized by using rf magnetron sputtering. The magnetic properties, crystalline structures, microstructures, and surface morphologies of the as-deposited samples were characterized using angle-resolved M–H loop tracer, VSM, XRD, TEM, AES and AFM. An evolution of the in-plane anisotropy was observed with the changing thickness of the nonmagnetic TaN interlayer in the FeTaN/TaN/FeTaN sandwiches, such as the easy-hard axis switching and the appearing of biaxial anisotropy. It is ascribed to three possible mechanisms, which are interlayer magnetic coupling, stress, and interface roughness, respectively. Interlayer coupling and stress anisotropies may be the major reasons to cause the easy–hard axis switching in the sandwiches whereas, magnetostatic and interface anisotropies may be the major reasons to cause biaxial anisotropy in the sandwiches, in which magnetostatic anisotropy is the dominant one.