Topological materials for helicity-dependent THz emission
Institute of Electrical and Electronics Engineers (IEEE) 00 (2023) 1-2
X-ray detected ferromagnetic resonance techniques for the study of magnetization dynamics
(2023)
Study of magnetic correlations in the magnetic topological insulator (Cr,Sb)2Te3
Physical Review B: Condensed Matter and Materials Physics American Physical Society 106 (2022) 224425
Abstract:
Chromium-doped Sb2Te3 is a magnetic topological insulator (MTI), which belongs to the (Sb,Bi)2(Se,Te)3 family. When doped with the transition metals V, Cr and Mn this family displays long-range ferromagnetic order above liquid nitrogen temperature and is currently intensely explored for quantum device applications. Despite the large magnetic ordering temperature, the experimental observation of dissipationless electrical transport channels, i.e., the quantum anomalous Hall effect, is limited in these materials to temperatures below ∼2 K. Inhomogeneities in the MTI have been identified as a major concern, affecting the coupling between the Dirac states and the magnetic dopants. Nevertheless, details on the local magnetic order in these materials are not well understood. Here, we report the study of the magnetic correlations in thin films using a combination of muon spin relaxation, and magnetic soft x-ray spectroscopy and imaging. µSR provides two key quantities for understanding the microscopic magnetic behavior: The magnetic volume fraction, i.e., the percentage of the material that is ferromagnetically ordered, and the relaxation rate, which is sensitive to the magnetic static (∼µs) and dynamic disorder. By choosing different implantationdepths for the muons, one can further discriminate between near-surface and bulk properties. No evidence for a surface enhancement of the magnetic ordering is observed, but, instead, we find evidence of small magnetically ordered clusters in a paramagnetic background, which are coupled. The significant magnetic field shift that is present in all samples indicates a percolation transition that proceeds through the formation and growth of magnetically ordered spin clusters. We further find that fluctuations are present even at low temperatures, and that there appears to be a transition between superparamagnetism and superferromagnetism.Polarization analysis by means of individual soft x-ray absorption spectra of rare earths
Physical Review B American Physical Society (APS) 106:21 (2022) 214423
Tailoring the magnetic exchange interaction in MnBi2 Te4 superlattices via the intercalation of ferromagnetic layers
Nature Electronics (2022)