Ferromagnetic percolation in MnxGe1-x dilute magnetic semiconductor -: art. no. 152507

We have studied the magnetic and magnetotransport properties of Mn-doped Ge grown by molecular-beam epitaxy. This group-IV dilute ferromagnetic semiconductor exhibits two magnetic transitions. An upper critical temperature T-C* (similar to 112 K for x similar to 0.05) is evident from the extrapolated Curie-Weiss susceptibility and from the Arrott plot analysis of anomalous Hall effect data. The existence of a lower critical temperature T-C (similar to 12 K for x similar to 0.05) is established from ac susceptibility and magnetotransport data. The data are fully compatible with the existence of bound magnetic polarons or clusters below T-C* which percolate at T-C << T-C*. (C) 2005 American Institute of Physics.