Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)
MA 13.110: Poster
Dienstag, 9. März 2004, 15:00–19:00, Bereich A
X-ray magnetic and natural circular dichroism above and below the Verwey transition in a Fe3O4 single crystal — •S. Gold, E. Goering, and G. Schütz — Max-Planck-Institut für Metallforschung, 70569 Stuttgart
Recently Fe3O4 has become an intensive studied system, due to its proposed and experimentally observed high spin polarization at the fermi energy and its related applicability in future spin electronic devices. In addition, at the so called Verwey transition, which has been investigated over many decades, a dramatic change in the electrical resistivity appears. We show detailed X-ray magnetic circular dichroism (XMCD) experiments at 1T applied magnetic field performed above and below the Verwey transition and along different crystallographic directions ((100), (110) and (111)). We have observed very small changes in the XMCD-spectra of this cubic system as a function of temperature and orientation, which has not been observed before in a cubic system. Changes in the differences of the projected orbital moments along the given crystallographic axes above and below the Verwey transition are consistent to the observed change of the easy axis. In addition a directly observable and unexpected large nonmagnetic natural circular dichroism (XNCD) signal has been observed by flipping the helicity of the synchrotron beam. This is a sign of an unexpected local non centro symmetric charge distribution at the 3d transition metal site. Our investigations give new insight to the microscopic ground state and excited state properties of Fe3O4 related to the magnetic behavior and the Verwey transition.