Polarization-modulation technique with diamond phase retarder to improve the accuracy of XMCD measurements

A polarization-modulation technique for accurate measurements of x-ray magn etic circular dichroism (XMCD) has been developed by combination of a diamo nd x-ray phase retarder and a phase-sensitive (lock-in) detection system. T he x-ray helicity was switched at 40 Hz by moving the phase retarder, and t he resulting variation in sample absorption was detected using an amplifier locked to the helicity-modulation frequency. The measured XMCD spectrum at the Fe K-edge in CoFe2O4 agreed with that obtained using a conventional ma gnetic-field-inversion method. The new technique provides higher statistica l accuracy in a shorter measuring time.