Magnetic polarons and large negative magnetoresistance in GaAs nanowires implanted with Mn ions.

Kumar, Sandeep; Paschoal, Waldomiro; Johannes, Andreas; Jacobsson, Daniel; Borschel, Christian; Pertsova, Anna; Wang, Chih-Han; Wu, Maw-Kuen et al. · Nano Lett · 2013

basic_science · Level V

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Abstract

We report on low-temperature magnetotransport and SQUID measurements on heavily doped Mn-implanted GaAs nanowires. SQUID data recorded at low magnetic fields exhibit clear signs of the onset of a spin-glass phase with a transition temperature of about 16 K. Magnetotransport experiments reveal a corresponding peak in resistance at 16 K and a large negative magnetoresistance, reaching 40% at 1.6 K and 8 T. The negative magnetoresistance decreases at elevated temperatures and vanishes at about 100 K. We interpret our transport data in terms of spin-dependent hopping in a complex magnetic nanowire landscape of magnetic polarons, separated by intermediate regions of Mn impurity spins, forming a paramagnetic/spin-glass phase.