AVS 51st International Symposium
    Semiconductors Monday Sessions
       Session SC+MI-MoM

Paper SC+MI-MoM11
Ferromagnetism and Polaron Percolation in Mn@sub x@Ge@sub 1-x@ Dilute Magnetic Semiconductor

Monday, November 15, 2004, 11:40 am, Room 304B

Session: Dilute Magnetic and Ferromagnetic Semiconductors
Presenter: A.P. Li, Oak Ridge National Laboratory
Authors: A.P. Li, Oak Ridge National Laboratory
J.F. Wendelken, Oak Ridge National Laboratory
J. Shen, Oak Ridge National Laboratory
J.R. Thompson, Oak Ridge National Laboratory, University of Tennessee
H.H. Weitering, Oak Ridge National Laboratory, University of Tennessee
Correspondent: Click to Email
In dilute magnetic semiconductors (DMS), ferromagnetic ordering is carrier mediated. This picture seems to be accepted more or less universally, but the detailed nature of the ferromagnetism varies greatly from system to system. We have studied ferromagnetism and the correlation between transport and ferromagnetism in Mn@sub x@Ge@sub 1-x@ DMS for Mn concentrations up to 9%. By carefully controlling the growth conditions, we obtained precipitate-free Mn@sub x@Ge@sub 1-x@ that exhibits magnetic phase transitions at Tc = 20 K and Tc* = 112 K. The magnetic response to temperature and doping concentration is indicative of a magnetic-polaron percolation transition at Tc [1], which coincides with a metal-insulator transition and Hall-effect sign anomaly. Tc* is the ferromagnetic ordering temperature within isolated polarons which can be determined from a Curie-Weiss plot of the high-temperature magnetic susceptibility. Ferromagnetism in Mn@sub x@Ge@sub 1-x@ DMS reveals a striking analogy with the magnetism of so-called "clustered states" in manganite compounds [2]. [1] A. Kaminski and S. Das Sarma, Phys. Rev. B 68, 235210 (2003) [2] G. Alvarez and E. Dagotto, Phys. Rev. B 68, 045202 (2003).