Study of magnetic materials using helicity-modulated X-ray magnetic circular dichroism.

A new helicity-modulation technique has been applied for recording X-ray magnetic circular dichroism (XMCD) at the K-absorption edge in transition-metal magnetic materials. This technique enables the measurement of the XMCD spectrum with high precision and under extreme conditions. The refined spectrum is presented at the Fe K edge for pure Fe, Fe4N and Co-ferrite. The method is very promising for site-assignment of magnetic cations and for detailed investigation of the magnetic states in a local environment. In Mn3MC perovskites, the dependence of the Mn K-edge XMCD spectrum on temperature and magnetic field demonstrates that the orbital moments are closely associated with the magnetic phase transition. New information obtained from the refined spectrum and novel phenomena observed in temperature and field variations is presented.