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Dresden 2014 – scientific programme

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MA: Fachverband Magnetismus

MA 11: Magnetic Heuslers, Half-metals and Oxides II (with TT)

MA 11.8: Talk

Monday, March 31, 2014, 17:30–17:45, BEY 118

NMR Investigation of Optimal Mn Content in Co2MnxSi0.88 Thin Films for High Tunneling Magneto-Resistance — •Steven Rodan1, Tomoyuki Taira2, Masafumi Yamamoto2, Bernd Büchner1,3, and Sabine Wurmehl1,31Leibniz Institute for Solid State and Materials Research, 01171 Dresden, Germany — 2Division of Electronics for Informatics, Hokkaido University, Sapporo 060-0814, Japan — 3Institute für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany

Half-metallic ferromagnets (HMFs), with 100% spin-polarized conduction electrons, are prime candidates for developing spintronics devices. Many Heusler compounds, such as Co2MnSi, are predicted to be HMFs. A technique for probing local structure such as nuclear magnetic resonance (NMR) is essential for understanding the microscopic origin of manifested physical properties. Local atomic disorder was investigated using both 59Co and 55Mn NMR on epitaxial films of Co2MnxSi0.88, with varying Mn content (x = 0.72, 1.12, 1.32). NMR spectra confirmed that the high tunneling magneto-resistance ratio values for magnetic tunnel junctions with electrodes made from highest Mn excess (x=0.32), can be attributed mainly to the reduction of Co antisites (Co on Mn and/or Si sites), which are expected to strongly decrease the half-metallicity.

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