Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.13: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU C

Digital Lock-In XMCD-experiments with a quarter wave plate — •Max Harlander, Jochen Geisler, Eberhard Goering, Uwe Grüner, Sebastian Macke und Gisela Schütz — Max-Planck-Insitut für Metallforschung, 70569 Stuttgart

We have developed an ultra low noise digital lock in technique, utilizing a diamond single crystal quarter wave plate. At the ANKA MPG diffraction beamline we have achieved a degree of circular polarisation above 85%.The diamond quarter wave plate is controlled and flipped with a square wave shaped modulation, with a ground frequency up to 80Hz, by a positional controlled piezo element. The related right and left polarised light absorption of the magnetized sample has been measured and recorded by an a/d-signal converting PC card. The sampled signals are numerically evaluated and analysed to obtain a digital lock-in-XMCD signal. FePt alloy measurements are in perfect agreement with conventional XMCD measurements. To demonstrate the capability of this method, XMCD and XAS spectra of an effective very small PtCo single crystal are shown. This improved method achieves a signal to noise ratio at the level of the pure photon statistics. Our system is portable and allows measurement at virtually any synchrotron radiation source.