Fluorescence-DetectedX-ray Magnetic CircularDichroism of Well-Defined MnIIand NiIIDopedin MgO Crystals: Credential Evaluation for Measurements on BiologicalSamples.

L2,3-edge X-ray magnetic circular dichroism(XMCD) spectrahave been measured for the well-defined dilute NiIIandMnIIions doped into a MgO crystal, with sub-Kelvin dilutionrefrigerator cooling and 2 T magnetic field magnetization. A 30-elementGe array X-ray detector has been used to measure the XMCD for thesedilute ions, whose concentrations are 1400 ppm for NiIIand 10 000 ppm for MnII. Large XMCD effects havebeen observed for both NiIIand MnII, and multipletsimulation described the observed spectra. The fluorescence-detectedL-edge absorption spectrum and XMCD of NiIIin MgO arecomparable with both theoretical calculations and the total electronyield measured ions in similar chemical environments, at least qualitativelyvalidating the use of the sensitive fluorescence detection techniquefor studying XMCD for dilute 3d metal ions, such as various metalloproteins.Sum rule analyses on the XMCD spectra are also performed. In addition,these XMCD measurements have also been used to obtain the sample’smagnetization curve and the beamline’s X-ray helicity curve.This study also illustrated that bend magnet beamlines are still usefulin examining XMCD on dilute and paramagnetic metal sites. [ABSTRACT FROM AUTHOR]