ABSTRACT
Abstract. Epitaxial films of the half-metallic ferromagnets C02M11AI and Co2MnGa were grown on GaAs substrates by MBE. The similar structure and close lattice matching to GaAs make them good candidates for spintronic devices. Magnetic and transport properties of the full Heusler alloys show several anomalous properties. Magnetization measurements yield ferromagnetic Curie temperatures of Tc~800-1000 K, illustrating that cobalt has a stronger exchange interaction compared to nickel-based materials, such as Ni2MnGa, having Curie temperatures in the range Tc~300-400 K. Measurements in the Hall geometry with the field applied perpendicular to the layers exhibit a giant Hall effect (GHE) at room temperature. The GHE is a result of the extraordinary Hall effect and is driven by the strong out-of-plane magnetization. Epitaxial Coi_xMnx films were also grown on GaAs. The range of ferromagnetism for epitaxially strained Coi_xMnx, film is found for xfm<0.7, unlike bulk alloys where x f m < 0.32.
