Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 8: Magnetic Materials II

MA 8.6: Vortrag

Montag, 26. März 2007, 16:30–16:45, H22

Mössbauer and NMR study of Heusler alloy Co₂Mn_1−xFe_xSi — •Vadim Ksenofontov¹, Hem Chandra Kandpal¹, Marek Wojcik², Benjamin Balke¹, and Claudia Felser¹ — ¹Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Staudinger Weg 9, 55099 Mainz, Germany — ²Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warszawa, Poland

The Heusler alloys Co₂Mn_1−xFe_xSi have recently attracted particular interest due to the unique possibility to tune the spin polarization by varying the Mn/Fe fraction. The calculated band structures show the shift of the Fermi energy from the top of the minority valence band for Co₂MnSi to the bottom of the minority conduction band for Co₂FeSi upon Fe doping. From computational results it has been predicted that a compound with an intermediate Fe concentration of about 50% should be best suited for spintronic applications. These theoretical findings still require experimental proofs. We report on ⁵⁷Fe Mössbauer spectroscopic, ⁵⁹Co and ⁵⁵Mn NMR studies of hyperfine magnetic fields (HFF) in Co₂Mn_1−xFe_xSi (0 ≤ x ≤ 1). The hyperfine magnetic field on Fe atoms is non-monotonic and shows maximum at x = 0.5. We argue that the maximum value of the HFF found on Fe and Co atoms at x = 0.5 is due to the existence of maximal spin-polarization in Co₂Mn_0.5Fe_0.5Si. Experimentally found HFF values are compared with results following from electronic band structure calculations taking into account electronic correlations (LDA+U).