Influence of the Si Substrate on the Transport and Magnetotransport Properties of Nanostructured Fe-Ag Thin Films

A systematic study of electrical and magnetic transport properties of ${\rm Fe}_{x}{\rm Ag}_{100-x}$ $(50≪x≪55)$ thin films deposited by both sputtering and pulsed laser ablation onto two $p$-type Si substrates with different resistivities is reported in this work. Resistance, magnetoresistance and Hall effect were measured in the temperature range 75–350 K. Magnetization was measured in the temperature range 5–300 K, showing no appreciable differences for samples deposited onto one substrate or the other. A near room temperature transition in the resistance has been observed only for samples deposited onto the lower resistance substrate. Before this transition, the results obtained agree well with the conduction being almost completely confined to the metallic film, but after the transition, apparently most of the carriers change to the substrate. This is corroborated by the positive magnetoresistance and the change in the sign of the carriers indicated by the Hall measurements after the transition. The experimental results agree well with a three layer model that includes an interface whose resistance increases exponentially with decreasing temperature.