Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

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

MA 11.8: Vortrag

Montag, 31. März 2014, 17:30–17:45, BEY 118

NMR Investigation of Optimal Mn Content in Co₂Mn_xSi_0.88 Thin Films for High Tunneling Magneto-Resistance — •Steven Rodan¹, Tomoyuki Taira², Masafumi Yamamoto², Bernd Büchner^1,3, and Sabine Wurmehl^1,3 — ¹Leibniz 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 Co₂Mn_xSi_0.88, 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.