title: Study of Dy-doped Bi₂Te₃: thin film growth and magnetic properties.
abstract: Breaking the time-reversal symmetry (TRS) in topological insulators (TIs) through ferromagnetic doping is an essential prerequisite for unlocking novel physical phenomena and exploring potential device applications. Here, we report the successful growth of high-quality (Dy(x)Bi(1-x))2Te3 thin films with Dy concentrations up to x = 0.355 by molecular beam epitaxy. Bulk-sensitive magnetisation studies using superconducting quantum interference device magnetometry find paramagnetic behaviour down to 2 K for the entire doping series. The effective magnetic moment, μeff, is strongly doping concentration-dependent and reduces from ∼12.6 μ(B) Dy(-1) for x = 0.023 to ∼4.3 μ(B) Dy(-1) for x = 0.355. X-ray absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Dy M4,5 edge are employed to provide a deeper insight into the magnetic nature of the Dy(3+)-doped films. XMCD, measured in surface-sensitive total-electron-yield detection, gives μ(eff )= 4.2 μ(B) Dy(-1). The large measured moments make Dy-doped films interesting TI systems in which the TRS may be broken via the proximity effect due to an adjacent ferromagnetic insulator.
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK. Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Harrison
authors.forename: L J
authors.initials: LJ
authors.lastname: Collins-McIntyre
authors.forename: S-L
authors.initials: SL
authors.lastname: Zhang
authors.forename: A A
authors.initials: AA
authors.lastname: Baker
authors.forename: A I
authors.initials: AI
authors.lastname: Figueroa
authors.forename: A J
authors.initials: AJ
authors.lastname: Kellock
authors.forename: A
authors.initials: A
authors.lastname: Pushp
authors.forename: S S P
authors.initials: SS
authors.lastname: Parkin
authors.forename: J S
authors.initials: JS
authors.lastname: Harris
authors.forename: G
authors.initials: G
authors.lastname: van der Laan
authors.forename: T
authors.initials: T
authors.lastname: Hesjedal