Ferromagnetic Topological Insulators – A Hot Topic

In the quest to find high-temperature ferromagnetic topological insulators (TIs), we have explored different transition-metal and rare-earth doped thin film and bulk samples using x-ray magnetic circular dichroism and polarized neutron reflectometry (PNR) at ISIS. In Cr-doped Sb2Te3 films magnetic transition temperatures of ~180 K have been found, a truly remarkable development compared to the sub-10-K TC’s seen before. Unfortunately, there are hints of a second magnetic phase for x > 0.42, which is not detectable in XRD for the low doping concentration samples, and the question is what the magnetic properties of the two phases are and which one is the desired phase for unlocking the exotic TI physics at high temperatures. Here, we propose to carry out a comparative study of V- and Cr-doped Sb2Te3 thin films, supported by magnetometry and structural investigations.