Magnetic properties of the new diluted magnetic semiconductor Zn1-xMnxAs2:: evidence of MnAs clusters

The preparation and magnetic properties of the diluted magnetic semiconductor Zn1-xMnxAs2, opening a novel group of II-V-2 compounds alloyed with transition metal elements, are reported for the first time; Single crystals of Zn1-xMnxAs2 are obtained with a modified Bridgman method. For x less than or equal to 0.2 their structure is isomorphic to the ZnAs2 parent compound. Magnetic properties of Zn1-xMnxAs2 are investigated for x = 0.01, 0.05 and 0.1 between T = 2 and 500 K in fields up to 60 kc. All the samples show a steep decrease of magnetization well above 300 K. In low fields (2-200 G) the temperature dependence of the magnetic susceptibility is strongly irreversible below T-b approximate to 250 K. The magnetization displays nonlinear field dependence starting from B similar to 1-2 kG and reaching full saturation above 40 kG. Its temperature dependence is weak between 2 and 300 K. The magnetic properties are explained by the presence of MnAs clusters. The distribution of cluster sizes is described by three overlapping Gaussian functions with the maxims at 1.7, 2.4 and 3.3 nm. At 300K the corresponding magnetic moments are found to be 1.5, 4.1 and 10.4 in units of 10(3) mu(B).