Solid-state reaction in Ti/Ni multilayered films studied by using magneto-optical spectroscopy

A comparative study of the solid-state reaction (SSR) in a series of Ti/Ni multilayered films (MLFs) with bilayer periods of 0.65-22.2 nm and a constant Ti to Ni sublayer thickness ratio was performed by using experimental and computer-simulated magneto-optical (MO) spectroscopy based on different models of MLFs, as well as x-ray diffraction (XRD). The spectral and sublayer-thickness dependences of the MO properties of the Ti/Ni MLFs were explained on the basis of the electromagnetic theory. The existence of a threshold nominal Ni-sublayer thickness of about 3 nm for the as-deposited Ti/Ni MLF to observe of the equatorial Kerr effect was explained by a solid-state reaction which formed nonmagnetic alloyed regions between pure components during the MLF deposition. The SSR in the Ti/Ni MLFs, which was caused by the low temperature annealing, led to the formation of an amorphous Ti-Ni alloy and took place mainly in the Ti/Ni MLFs with "thick" sublayers. For the case of Ti/Ni MLFs, the MO approach turned out to be more sensitive in determining the thickness of the reacted zone, while XRD was more useful for the structural analysis. It was also suggested that very thin non-reacted Ni sublayers had different MO properties from those of the bulk.