Microstructure, electrical, magnetic, and extraordinary Hall effect studies in Ni:SiO2 nanogranular films synthesized by atom beam sputtering

In this work we report on the synthesis of Ni:SiO2 nanogranular films with different metal fraction (0.10≤x≤0.68)and a homogeneous distribution of Ni particles by atom beam sputtering technique and on the study of their microstructure, electrical transport, magnetic properties, and on the observation of extraordinary Hall effect (EHE). Films with the Ni fraction x above percolation threshold (x≥0.58>xp) as revealed by resistivity versus temperature measurements have a large Ni particle size, pronounced ferromagnetic characteristics, and appreciable extraordinary Hall resistivity at 300 K. Furthermore, films above percolation have a relatively low, nearly temperature independent Ohmic resistivity smaller than 10−3 Ω cm and may be useful for Hall sensor applications. On the other hand, films below percolation threshold (x≤0.54<xp) have a small Ni particle size, superparamagnetic behavior, and do not show EHE at 300 K. However, at 5 K all films (xxp) show ferromagnetic characteristics with an enhanced EHE.