Dresden 2009 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 28: Electronic Properties I

MM 28.4: Talk

Wednesday, March 25, 2009, 11:00–11:15, IFW D

Co_xFe_(x−1)S₂: How close to half-metallicity? — •C. Utfeld¹, S. R. Giblin², J. W. Taylor², J. Laverock¹, S. B. Dugdale¹, C. Shenton-Taylor³, J. A. Duffy³, L. Wang⁴, C. Leighton⁴, M. Itou⁵, and Y. Sakurai⁵ — ¹H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK — ²ISIS Facility, RAL, Chilton, Oxfordshire OX11 0QX, UK — ³Department of Physics, University of Warwick, Coventry CV4 7AL, UK — ⁴Chem. Eng. & Mat. Sci., University of Minnesota, Minneapolis, MN 55455, USA — ⁵SPring-8, 1-1-1 Kouto, Mikazuki, Sayo, Hyogo 679-5198, Japan

CoS₂ is a material thought to be very close to being a half-metal, i.e. to only be conducting in one spin. However, the Fermi level lies low in the conduction bands and doping with the isostructural semiconductor FeS₂ is predicted to gradually unoccupy one spin channel. In this context the evolution of the polarisation across the series Co_xFe_(1−x)S₂ is of major interest. Experimentally the number of direct measurements accessing the bulk polarisation for different alloy compositions is rather limited. We present a magnetic Compton scattering study combined with ab initio calculations as a method to determine the bulk spin polarisation in CoS₂ and Co_0.9Fe_0.1S₂. Magnetic Compton scattering is a versatile technique for investigations into spin-dependent bulk properties because it probes the unpaired electrons directly. We compare the data with theoretical predictions and optimise the agreement by rigidly shifting the bands in order to extract the tuned bulk polarisations of P≈-75% and P≈18% for the pure and the x=0.1 system, respectively.