Investigation of local magnetic moment fluctuations and their correlation with topological insulating behaviour of transition metal doped Sb2Te3

While a magnetic topological Insulator (MTI) has enormous application potential, the retention of magnetism in a topological insulator (TI) is challenging. Transition metal (TM) dopants can be used to modify the defect concentration and induce disorder in the TI, Sb2Te3. Our measurements reveal that the hole (major carrier) contribution is supressed by TM (=Fe, Co, Ni) doping in pristine Sb2Te3. The higher resistivity of all TM doped samples, viz, Sb1.97TM0.03Te3 also demonstrates that magnetic doping increases the bulk insulating behaviour of Sb2Te3. A low carrier concentration and high resistivity have been identified as two significant features for retaining TI behaviour. Here, we will exploit Muon spectroscopy to investigate changes in local magnetism and its correlation with TI properties in TM-doped Sb2Te3. Characterizing the both the static and dynamic fluctuations of the magnetic moments will provide new insights into the impact of the TM dopant on the local magnetic structure of a TI material.