Magnetic and transport properties of Ga1-xMnxAs, a new III-V diluted magnetic semiconductor

Gal.,Mn,As is a new III-V diluted magnetic semiconductor that can be grown by MBE with Mn concentrations up to x approximate to 0.09. Below a critical temperature T-c, determined by the Mn concentration (about 50 K for x = 0.05) the material becomes ferromagnetic. This is attributed to the magnetic long-range order of Mn-hole complexes, the latter being the result of the strong antiferromagnetic interaction between the holes and Mn 3d spins. Transport and magnetic properties of the Ga1-xMnxAs system are strongly correlated. Above T-c, all samples show transport behaviour characteristic for materials near the metal insulator transition. Below T-c, resistivity decreases as the magnetic ordering sets in. When the magnetisation has reached its saturation value (below similar to 20 K), variable range hopping is the main transport mechanism. Also, a negative magnetoresistance is observed below T-c.