Normal and reversed tunable magnetoresistance in a NiOx/p-doped silicon diode

Abstract

Nonstoichiometric NiOx thin films fabricated by heating in air nickel thin films sputtered on p-doped silicon substrates show a superparamagnetic magnetization and frustrated magnetism with transition temperatures of 200–300 K. Transport measurements across the magnetic/semiconductor bilayer have a rectifying I-V and voltage dependent magnetoresistance, with maximum ratios at 77 K and 2 T of 70% and −17%. The effect is explained in terms of field dependent polarization in granular NiOx and highly efficient spin filtering/injection.