Magnetotransport in phase-separated (Ga,Fe)N with γ′−GayFe4−yN nanocrystals

Abstract

The magnetotransport in phase-separated (Ga,Fe)N containing ${\gamma }^{\prime }\text{−}{\mathrm{Ga}}_y{\mathrm{Fe}}_{4-y}\mathrm{N}$ ($0<y<1$) nanocrystals (NCs) is studied in the temperature range between 2 and 300 K. The evolution of the resistivity and of the magnetoresistance (MR) as a function of temperature points to two conduction mechanisms, namely, a conventional Arrhenius-type one down to 50 K and Mott variable range hopping at lower temperatures, where the spin-polarized current is transported between NCs in a regime in which phonon-scattering effects are not dominant. Below 25 K, the MR shows a hysteretic contribution at magnetic fields $<1\mathrm{T}$ and proportional to the coercive field. Anisotropic magnetoresistance with values one order of magnitude greater than those previously reported for ${\gamma }^{\prime }\text{−}{\mathrm{Fe}}_4\mathrm{N}$ thin films over the whole considered temperature range confirms that the observed MR in these layers is determined by the embedded nanocrystals.