Transport and magnetic properties of the diluted magnetic semiconductors Sb1.98-xV0.02CrxTe3 and Sb1.984-yV0.016MnyTe3

We report on electrical transport and magnetic properties of quaternary single crystals of Sb1.98-xV0.02CrxTe3 and Sb1.984-yV0.016MnyTe3 with x ranging from 0 to 0.022 and y ranging from 0 to 0.034 over temperatures from 2 K to 300 K. Ternary crystals Sb2-zVzTe3 were reported to have rather small magnetization in the ferromagnetic state due to low spin of vanadium ions. Therefore, we attempted to combine vanadium with other high-spin elements hoping to enhance both magnetization and the Curie temperature of these diluted magnetic semiconductors (DMS) based on the Sb2Te3 matrix. While the Curie temperatures of Sb198-xV0.02CrxTe3 samples are comparable to that of Sb1.98V0.02Te3, we observe a significant enhancement in the remanent magnetization when Cr is co-doped. In contrast, adding Mn to Sb1.984V0.016Te3 leads to a decrease in the Curie temperature and, at higher concentrations, to a complete suppression of ferromagnetism. Since Mn enhances the concentration of holes, its presence might seem favorable to the formation of the ferromagnetic order. In reality, the destruction of ferromagnetism in samples containing Mn is likely a result of the antiferromagnetically coupled Mn-ion pairs. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.