Thermomagnetic behaviour and compositional irreversibility on (Fe/Si) sub(3) multilayer films

This work presents the correlation between the morphology and magnetic properties of (Fe/Si) sub(3) multilayers with different Fe layer thicknesses and fixed Si spacer thickness in a broad temperature range (5 < T < 800 K). Films were prepared by thermal evaporation under ultrahigh vacuum onto a buffer layer of Fe/Ag deposited on a GaAs(001) substrate. Transmission electron microscopy reveals good epitaxial growth and phase transformations in the c-FeSi phase formed during deposition as well as upon subsequent annealing of the sample up to 800 K. Remanence to saturation magnetization M sub(R)M sub(S)ratios and saturation fields are related to several types of interlayer exchange coupling. 90 parallel -coupling and a superposition of 90 parallel and antiferromagnetic interlayer exchange coupling are found depending on the Fe layer thickness. Magnetization curves were investigated as a function of temperature by in situ annealing. They show an irreversible thermal process as temperature increases from 300 to 450 K that is correlated to the formation of a ferromagnetic silicide phase. At higher temperature this phase transforms into a paramagnetic Fe-Si phase.