Study of interfacial properties and its effect on magnetization behaviour of Fe/Ni multilayer structure

Abstract

This paper deals with the investigation of interfacial properties and their influence on magnetization behaviour of Fe/Ni multilayer (ML) structures. Two types of multilayer structures with nominal composition of [Fe(29Å)/Ni(86Å)]10 and [Fe(50Å)/Ni(50Å)]10 were prepared with e-beam evaporation technique under ultra high vacuum (UHV) conditions. Grazing incidence X-ray reflectivity (GIXRR) and X-ray diffraction (GIXRD) techniques have been employed to determine the micro-structural parameters and indicates formation of FeNi3 alloy phase at the interface. GIXRD measurements on as-deposited Fe50/Ni50 ML samples show highly textured growth and its structure remains the same upto annealing temperature of 350°C. The magnetization behavior of the MLs has been obtained using extraction dc magnetometry. The M–H loops corresponding to the Fe50/Ni50ML structure of as-deposited sample show gradual changes with applied field whereas the as-deposited Fe29/Ni86ML shows a perfectly square loop. Upon annealing of the Fe29/Ni86MLs upto 300°C show change in the loop shape from square to the smoother one. This is mainly attributed to release of stress in deposited layer and the change in magnetostriction. However, square loops observed in this case at higher annealing temperature of 300 and 400°C is result of magnetically soft FeNi3 phase formation at interface. On the other hand, Fe50/Ni50ML samples annealed upto 400°C show no change in the shape even though there is variation in HC values. The observed changes in the HC values are mainly attributed in this case to the different magnetostriction effects involved due to the increase in grain size with temperature.