  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.
