Letter abstract

Nature Physics 6, 22 - 25 (2010)
Published online: 15 November 2009 | doi:10.1038/nphys1455

Subject Category: Condensed-matter physics

Experimental probing of the interplay between ferromagnetism and localization in (Ga, Mn)As

Maciej Sawicki1,2, Daichi Chiba1,3, Anna Korbecka4, Yu Nishitani1, Jacek A. Majewski4, Fumihiro Matsukura1,3, Tomasz Dietl2,3,4 & Hideo Ohno1,3


The question of whether the Anderson–Mott localization enhances or reduces magnetic correlations is central to the physics of magnetic alloys1. Particularly intriguing is the case of (Ga, Mn)As and related magnetic semiconductors, for which diverging theoretical scenarios have been proposed2, 3, 4, 5, 6, 7, 8, 9. Here, by direct magnetization 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 models3, 5, 8, 9. We find that the transition from the ferromagnetic to the paramagnetic state proceeds by means of the emergence of a superparamagnetic-like spin arrangement. This implies that carrier localization leads to a phase separation into ferromagnetic and non-magnetic regions, which we attribute to critical fluctuations in the local density of states, specific to the Anderson–Mott quantum transition.

  1. Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
  2. Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02 668 Warszawa, Poland
  3. Semiconductor Spintronics Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Sanban-cho 5, Chiyoda-ku, Tokyo 102-0075, Japan
  4. Institute of Theoretical Physics, University of Warsaw, ul. Hoża 69, PL 00 681 Warszawa, Poland

Correspondence to: Maciej Sawicki1,2 e-mail: mikes@ifpan.edu.pl


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