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 ^° C reduces H_C largely and annihilates the strip domains. On further increasing T_A, H_C increases initially at 300 ^° C and reduces slightly for 400 ^° 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 ^° 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.