Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 32: Magnetic Imaging

MA 32.5: Talk

Friday, March 30, 2007, 12:00–12:15, H22

Complex surface spin structure of equiatomic NiMn alloy — •Chunlei Gao¹, Aimo Winkelmann¹, Arthur Ernst¹, Jürgen Henk¹, Wulf Wulfhekel^1,2, and Jürgen Kirschner¹ — ¹Max-Planck-Institut für Mikrostrukturphysik Weinberg 2, D-06120 Halle, Germany — ²Physikalisches Institut, Universität Karlsruhe, Wolfgang-Gaede Strasse 1, 76131 Karlsruhe, Germany

Chemically ordered equiatomic NiMn thin films were epitaxially grown on Cu(001) by co-evaporation with Mn and Ni atoms occupying alternating atomic sheets perpendicular to the surface. In our experiments, the structure of NiMn/Cu(001) was investigated with low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). A p(2×2) reconstruction of the surface atoms was found with I-V LEED and atomically resolved STM measurements. The surface spin structure was studied with spin-polarized STM (Sp-STM) operating in the differential magnetic mode. The spin contrast arising from the different spin polarizations of Ni and Mn atoms was observed on the atomic scale. A strong voltage dependence of the spin unit cell was found which implies a complex noncollinear spin structure of the surface. Ab-initio calculations of the magnetic structure of NiMn thin films give a good agreement with the experimental observations.