Spin-fluctuation mediated high-temperature ferromagnetism in Si:Mn dilute magnetic semiconductors
RRC Kurchatov Institute, Kurchatov Sqr. 1, 123182 Moscow, Russia
2 SMC-INFM-CNR and Dipartimento di Fisica, Università di Roma “La Sapienza”, piazzale Aldo Moro 2, 00185 Roma, Italy
Corresponding author: a email@example.com
Published online: 22 September 2010
We discuss a possible route to explain high-temperature ferromagnetism in Si:Mn dilute magnetic semiconductors. We argue that most Mn atoms are segregated within nanometer-sized regions of magnetic precipitate and form the alloy, or compound, MnSi2-z with z ≈ (0.250.30), whereas a small minority of Mn atoms forms Ångström-sized magnetic defects embedded in the host. Assuming that MnSi2-z is a weak itinerant ferromagnet which supports sizable spin fluctuations (paramagnons) far above the intrinsic Curie temperature, we show that the Stoner enhancement of the exchange interaction between the local magnetic moments of the defects occurs. As a result, a significant increase of the temperature of global ferromagnetic order in the system is achieved. We develop a phenomenological approach, to qualitatively describe this effect.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010