Sign reversal of magnetoresistance in a perovskite nickelate by electron doping

Abstract

We present low temperature resistivity and magnetotransport measurements conducted on pristine and electron doped ${\mathrm{SmNiO}}_{3}$ (SNO). The low temperature transport in both pristine and electron-doped SNO shows a Mott variable range hopping with a substantial decrease in localization length of carriers by one order in the case of doped samples. Undoped SNO films show a negative magnetoresistance (MR) at all temperatures characterized by spin fluctuations with the evolution of a positive cusp at low temperatures. In striking contrast, upon electron doping of the films via hydrogenation, we observe a crossover to a linear nonsaturating positive $\mathrm{MR}\ensuremath{\sim}0.2%$ at 50 K. The results signify the role of localization phenomena in tuning the magnetotransport response in doped nickelates. Ionic doping is therefore a promising approach to tune magnetotransport in correlated perovskites.