Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 60: Magnetic Materials: Applications and Multielement Bulk Materials

MA 60.3: Vortrag

Freitag, 24. März 2017, 10:00–10:15, HSZ 101

Interplay of localization and magnetism in (Ga,Mn)As and (In,Mn)As — •Ye Yuan¹, Maciej Sawicki², Tomasz Dietl^2,3,4, Manfred Helm¹, and Shengqiang Zhou¹ — ¹Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany — ²Institute of Physics, Warsaw, Poland — ³Faculty of Physics, University of Warsaw, Warsaw, Poland — ⁴WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, Japan

We examine the role of localization on the hole-mediated ferromagnetism in dilute ferromagnetic semiconductors by combining results of electrical and magnetic studies for Mn-implanted GaAs and InAs. In both materials upon increasing the Mn concentration, a change from an insulating (hopping) regime of conductivity to a metallic-like is accompanied by a gradual build-up of a long-range magnetic coupling and a monotonic increase of the Curie temperature. For the least conducting sample no (global) Curie temperature can be identified, although the observed slow dynamics (superparamagnetic-like) confirms the presence of a ferromagnetic coupling acting only over limited (mesoscopic) distances. Our findings strongly advocate for the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions between diluted spins even on the insulator side of the metal-to-insulator transition. This constitutes a new experimental support for the suggestion that larger p-d coupling results in higher values of TC only in the regime, where hole localization effects are not crucial.