ABSTRACT
Unlike Ga1-x MnxAs, Ga1-x Mn x Sb has proven to be difficult for realizing robust ferromagnetism. The first observed strong ferromagnetism in GaSb-based materials was in GaSb/Mn digital alloys, which were characterized by a two-phase behavior. We report a systematic study of Ga1-x Mn x Sb random alloys grown by molecular beam epitaxy. The magnetic properties of the samples showed a strong dependence on growth conditions, Sb/Ga flux ratio in particular. Nearly square-like hysteresis loops were observed for optimized flux ratios. Very large coercive fields were observed, up to 1000 Oe at 2 K. Magneto transport properties of the samples were also found to depend on the growth conditions, ranging from thermally activated conduction, indicative of a hopping conduction mechanism, to metallic behavior. A change of the slope (even the sign) of the Hall resistance vs. field as a function of temperature below Tc was observed in samples exhibiting hopping conduction. This change is discussed in terms of the position of the Fermi level relative to the impurity band.
