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MA: Fachverband Magnetismus

MA 4: Magnetic Heuslers, Half-metals and Oxides I (with TT)

MA 4.7: Vortrag

Montag, 31. März 2014, 11:00–11:15, BEY 118

Growth and physical properties of off-stoichiometric Co2Cr0.4Fe0.4Al1.2 Heusler compound — •Ahmad Omar, Marcel Haft, Jan Trinckauf, Christian G.F. Blum, Wolfgang Löser, Silke Hampel, Jochen Geck, Bernd Büchner, and Sabine Wurmehl — Leibniz Institute for Solid State and Materials Research IFW Dresden, Germany

Many Heusler compounds are predicted to be half-metallic ferromagnets and find extensive interest as materials for spintronic applications. Co2Cr0.6Fe0.4Al has been predicted to be 100% spin polarized, but so far, bulk samples as well as thin films do not verify those predictions and various results are fraught with anomalies. Recently, it has been shown that the underlying thermodynamic instability leads to phase transformation via spinodal decomposition in the material. The evolving secondary phase strongly affects the physical properties including spin polarization. One possible way to avoid the spinodal decomposition is to move in the phase diagram and thus avoid the immiscibility gap. We have grown off-stoichiometric Co2Cr0.4Fe0.4Al1.2 composition using optical Floating Zone (FZ) technique, which is known to be the technique of choice for incongruent melting systems such as materials in the Co-Cr- Fe-Al system. We do not observe any spinodal decomposition in our sample. The physical property measurements also match nicely with the theory, which has so far not been possible for Co2Cr1-xFexAl series. We have also performed X-ray Magnetic Circular Dichroism (XMCD) measurements on the sample which are promising compared to the band structure calculations.