Correlation Between Magnetic Ordering and Crossover from Weak Anti-Localization (WAL) to Weak Localization (WL) in Cobalt- and Manganese-Doped Bi0.94Sb0.06 Topological Insulator Nanoparticles

The discovery of magnetically doped topological insulators (TIs) provides a strong platform for investigating the correlation between long-range ferromagnetic/antiferromagnetic (FM/AFM) ordering and low temperature electron interference phenomena like weak anti-localization (WAL) or weak localization (WL). One such TI material Bi 1−x Sb x , which has recently been realised as a potential topological material for spintronics, has been studied in the present work. Influence of magnetic doping such as cobalt (Co) and manganese (Mn) in structural, morphological and magneto-transport properties on Bi 0.94 Sb 0.06 nanoparticles has been investigated. The focus was on studying the correlation between magnetic ordering and WAL/WL. In undoped sample for temperatures up to 5K, field dependent magneto resistance (MR) shows a prominent WAL dip around zero field demonstrating the presence of surface states. In both the Co- and Mn-doped samples, the WAL feature is destroyed indicating the absence of time reversal symmetry (TRS) in the system on doping. Interestingly, in the case of 49% manganese (Mn) doping, a clear crossover from WAL to WL has been observed in the MR alongside magnetic ordering and is evident from magnetic force microscopy as well.