Annealing Effects on the Structure and Magnetic Properties of Ni /Ti Multilayers

Interface of Ni/Ti multilayers deposited by dc triode sputtering under high purity conditions (base pressure 10 exp --7 torr plus getter-sputtering) and their thermal evolution are studied. This was achieved by combining high energy electron diffraction, secondary ion mass spectrometry and magnetometry. The study shows the existence of a non-magnetic interfacial amorphous layer due to interdiffusion over very short distances during deposition. A marked asymmetry between the two sides of a given layer is observed, due to interfacial contamination of titanium by carbon and oxygen acting as a diffusion barrier. Annealing treatments yield an increase in amorphization and finally crystallization of the interfacial amorphous phase to a NiTi stable phase.