Magnetic and electronic transport percolation in epitaxial GeMn films

TL;DR

This study investigates the magnetic and electronic transport properties of epitaxial GeMn films, revealing a percolation mechanism driven by bound magnetic polarons that influences resistivity and magnetic order.

Contribution

It provides experimental evidence for a percolation mechanism involving bound magnetic polarons in GeMn diluted magnetic semiconductors, linking transport and magnetic behaviors.

Findings

Resistivity shows insulator-like behavior with two activation energies.

A sudden resistivity reduction occurs at a characteristic temperature TR.

Magnetic order decreases with temperature, with Curie temperature near TR.

Abstract

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. Resistivity exhibits an insulator-like 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. 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 percolation 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)].