Composites based on self-assembled MnAs ferromagnet nanoclusters embedded in ZnSnAs2 semiconductor

Three self-assembled nanogranular composites based on MnAs ferromagnetic inclusions embedded in ZnSnAs2 semiconductors with MnAs concentration 10, 20, 47 mol.% were synthesized. The samples were studied by X-ray, SEM, AFM, MFM and SQUID methods. It has been shown that the increasing of the MnAs concentration in composite leads to slightly increasing of the size of the magnetic inclusions. Their size depends mainly on the speed of the crystallization, but the shape of the inclusions depends on the type of the interaction between materials. The connection between equilibrium and non-equilibrium structure of the compounds has been demonstrated. Magnetic properties of the ZnSnAs2 + MnAs samples show ferromagnetic phase transition with the Curie temperature having values from 313 K to 336 K, increasing as a function of the MnAs concentration in the nanocomposite. A small paramagnetic signal is observed at low temperatures due to individual Mn ions randomly distributed in the ZnSnAs2 lattice. All our samples show only a narrow magnetic hysteresis loop except of the sample with 47 mol.% of MnAs, for which the coercive field increases to about 120 G. The carrier transport of the alloy shows significant influence of the MnAs clusters. All our samples have p-type conductivity with magneto-transport strongly influenced by the presence of the MnAs phase in the nanocomposite samples. The magnetoresistance ( MR) of the alloy shows a complex behavior. The grain boundaries and MnAs clusters influence on the amplitude, sign, and temperature of MR. (C) 2015 Elsevier B.V. All rights reserved.