Magnetic and electronic transport percolation in epitaxial Ge1-xMnx films

Electronic transport and magnetic properties of Ge1–xMnx / Ge 100 films are investigated as a function of Mn dilution. Depending on x, characteristic temperatures separate different regimes in both properties. Resis- tivity exhibits an insulatorlike behavior in the whole temperature range and, below about 80 K, two distinct activation energies are observed. At a higher temperature value, TR, resistivity experiences a sudden reduction. The Hall coefficient shows a strong contribution from the anomalous Hall effect and, at TR, a sign inversion, from positive to negative, is recorded. The magnetic properties, inferred from magneto-optical Kerr effect, evidence a progressive decrease of the ferromagnetic long range order as the temperature is raised, with a Curie temperature TC not far from TR. The transport and magnetic results are qualitatively consistent with a perco- lation mechanism due to bound magnetic polarons in a GeMn diluted magnetic semiconductor, with localized holes (A. Kaminski and S. Das Sarma, Phys. Rev. B 68, 235210 2003.)