2009/09/21 by Maciej Sawicki, M. Sawicki, Daichi Chiba +8 · 5 citations
Materials Science · Physics and Astronomy · #Electronic and Structural Properties of Oxides #Magnetic and transport properties of perovskites and related materials #ZnO doping and properties #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/nphys1455
published as Nature Physics vol 6, 1 (2010) 22-25 · 8 pages, 3 figures
arxiv created 2009/09/21 · openalex publication_date 2009/11/15 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/29
The question whether the Anderson-Mott localisation enhances or reduces magnetic correlations is central to the physics of magnetic alloys. Particularly intriguing is the case of (Ga,Mn)As and related magnetic semiconductors, for which diverging theoretical scenarios have been proposed. Here, by direct magnetisation measurements we demonstrate how magnetism evolves when the density of carriers mediating the spin-spin coupling is diminished by the gate electric field in metal/insulator/semiconductor structures of (Ga,Mn)As. Our findings show that the channel depletion results in a monotonic decrease of the Curie temperature, with no evidence for the maximum expected within the impurity-band models. We find that the transition from the ferromagnetic to the paramagnetic state proceeds via the emergence of a superparamagnetic-like spin arrangement. This implies that carrier localisation leads to a phase separation into ferromagnetic and nonmagnetic regions, which we attribute to critical fluctuations in the local density of states, specific to the Anderson-Mott quantum transition.