X-ray magnetic circular dichroism study of Dy-doped Bi2Te3 topological insulator thin films

Journal article

Magnetic doping of topological insulators (TIs) is crucial for unlocking novel quantum phenomena, paving the way for spintronics applications. Recently, we have shown that doping with rare earth ions introduces large magnetic moments and allows for high doping concentrations without the loss of crystal quality, however no long range magnetic order was observed. In Dy-doped Bi2Te3 we found a band gap opening above a critical doping concentration, despite the paramagnetic bulk behavior. Here, we present a surface-sensitive x-ray magnetic circular dichroism (XMCD) study of an in situ cleaved lm in the cleanest possible environment. The Dy M4;5 absorption spectra measured with circularly polarized x-rays are tied using multiplet calculations to obtain the e ective magnetic moment. Arnott-Noakes plots, measured by the Dy M5 XMCD as a function of field at low temperatures, give a negative transition temperature. The evaporation of a ferromagnetic Co thin lm did not introduce ferromagnetic ordering of the Dy dopants either; instead a lowering of the transition temperature was observed, pointing towards an antiferromagnetic ordering scenario. This result shows that there is a competition between the magnetic exchange interaction and the Zeeman interaction. The latter favors the Co and Dy magnetic moments to be both aligned along the direction of the applied magnetic eld, while the exchange interaction is minimized if the Dy and Co atoms are antiferromagnetically coupled, as in zero applied field.

Authors: Figueroa, A; Baker, A; Harrison, S; Kummer, K; van der Laan, G

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Journal of Magnetism and Magnetic Materials
• Volume: 422
• Pages: 93-99
• Publication date: 2016-08-24
• Acceptance date: 2016-08-21
• DOI: 10.1016/j.jmmm.2016.08.063
• ISSN: 0304-8853
• Keywords: Article