Magnetic properties of clusters in IV-VI and II-IV-V2 diluted magnetic semiconductors

We have been studying magnetic properties of magnetic ion clusters in ternary, quaternary, and quinary IV-VI and II-IV-V2 diluted magnetic semiconductors with varying concentrations of different magnetic and non-magnetic cations. We observed clusters of different types, from non-random distribution of magnetic ions in the host lattice to precipitates with the crystalline structure different from that of the host. The size of such precipitates varied from 200 nm to 20 μm. Depending on the type and size of clusters we observed different magnetic properties of the compounds, such as paramagnetic, spin-glass, spin-glass-like, or ferromagnetic states. For example, Zn1-xMnxGeAs2 compounds with x ≤ 0.053 were paramagnetic with evidence of small short-range magnetic interactions, while in the same material with x ≥ 0.078 we observed room-temperature ferromagnetism. In IV-VI DMS clusters usually created a spin-glass or spinglass- like state. However, in some Ge1-x-yPbxMnyTe crystals we observed a co-existence of two very different spin-glasslike states with transition temperatures T1 ≈ 5 K and T2 ≈ 90 K.