Ferromagnetism and anomalous Hall effect in CoxGe1-x

Abstract

We report the growth of Co-doped Ge (CoxGe1-x) thin films by low-temperature molecular-beam epitaxy and the ferromagnetic properties without any additional carrier doping. The as-grown Co0.02Ge 0.98 has a Curie temperature, Tc-15 K, while those Co xGe1-x with x≥4.0 at. % are ferromagnetic above room temperature. On the other hand, Co0.02Ge0.98 exhibit ferromagnetic ordering up to Tc-150±10 K after a low-temperature annealing. A redshift in the Raman Ge-Ge mode was observed, indicating the substitution of Ge with Co atoms. The measured Co 0.02Ge0.98 are of p type and exhibit pronounced anomalous Hall effects. © 2006 American Institute of Physics.