Inverse magnetoresistance in Fe/Si ion beam sputtered sandwiches

Abstract

A series of Fe/Si sandwiches have been prepared by ion beam sputtering at room temperature onto glass substrate with the following nomenclature: Glass/Si20 nm/Fe5/6 nm/Fe5 nm/Ru2 nm. Magnetization measurements have been performed at 300 K and show no evidence of antiferromagnetic exchange coupling. However, the magnetoresistance curves recorded at 300 K are very interesting and show an inverse magnetoresistance for sandwiches with Si spacer layer thicknesses between 1.2 and 1.5 nm. The resistance is smaller at zero field than at saturation. This inverse magnetoresistance is due to the superparamagnetic interfaces and finds its origin in the difference of the electronic nature of the Fe/Si interfaces and Fe/Ru interfaces. Fe1−xSix iron silicide at Fe/Si interfaces has a scattering spin asymmetry ratio (α=ρ↓/ρ↑) larger than one, whereas, Fe with Ru impurities at the Fe/Ru interfaces presents a scattering spin asymmetry ratio smaller than one.