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

DOI: 10.1016/j.jmmm.2016.08.063 DOI Help

Authors: A. I. Figueroa (Diamond Light Source) , A. A. Baker (Diamond Light Source) , S. E. Harrison (Stanford University) , K. Kummer (European Synchrotron Radiation Facility (ESRF)) , G. Van Der Laan (Diamond Light Source) , T. Hesjedal (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Magnetism And Magnetic Materials

State: Published (Approved)
Published: November 2016
Diamond Proposal Number(s): 10207

Open Access Open Access

Abstract: 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 film in the cleanest possible environment. The Dy M4,5 absorption spectra measured with circularly polarized x-rays are fitted using multiplet calculations to obtain the effective magnetic moment. Arrott-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 film 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 field, while the exchange interaction is minimized if the Dy and Co atoms are antiferromagnetically coupled, as in zero applied field.

Journal Keywords: Topological insulators, Magnetic doping, Magnetic spectroscopy, XMCD, Molecular beam epitaxy

Subject Areas: Physics, Materials, Information and Communication Technology

Diamond Offline Facilities: SQUID-VSM Magnetometer (Quantum Design)
Instruments: I10-Beamline for Advanced Dichroism

Other Facilities: ESRF beamline ID32