Effect of Postannealing and Multilayer Structure on Soft Magnetic Properties of FeTaC Thin Film

We report a systematic investigation on room temperature and temperature dependent magnetic properties of [Fe-Ta-C(y)/Ta(1 nm](n=0-4)/FeTaC(y)/substrate] films prepared on thermally oxidized Si substrates at ambient temperature and postannealed at different temperatures (T-A) for 30 minutes. All the as-made films exhibit amorphous structure. The stripe domain structure with a large coercivity (H-C) observed in FeTaC (200 nm) single layer film due to stress induced during film deposition transforms to in-plane orientation of magnetization with multilayer structure. Postannealing at 200 degrees C reduces H-C largely and annihilates the strip domains. On further increasing T-A, H-C increases initially at 300 degrees C and reduces slightly for 400 degrees C annealed films. Also, the values of H-C strongly depend on the number of multilayers. The magnetization reversal process of multilayer films annealed above 250 degrees C depicts multistep reversal behavior due to an individual switching of ferromagnetic layer. High temperature thermomagnetization studies display a strong dependence of Curie temperature on T-A and multilayer structure. The observed results are discussed on the basis of stress-induced perpendicular anisotropy developed during film deposition, topological coupling at the interface, and magnetostatic interaction between the ferromagnetic layers.