Ground and Excited State Spin Configurations Probed by X-Ray Magnetic Circular Dichroism


Dr. Dario A. Arena
U4B Magnetic Materials Characterization Facility
National Synchrotron Light Source, Brookhaven National Laboratory


Since the pioneering experiments of Michael Faraday in the 19th century, techniques based on the interaction of magnetism and polarized light have had great success and extensive application.  One such technique, X-Ray Magnetic Circular Dichroism (XMCD), has been used over the past 25+ years to examine a wide range of issues such as quenching of the orbital moment in transition-metal ferromagnets, magnetic anisotropies, spin-reorientation transitions, and magnetic coupling mechanisms.  XMCD provides a unique perspective on ferromagnetism (FM) in elemental ferromagnets (e.g., Fe, Co, Ni) and is particularly useful in examining more complex materials, including compound ferromagnets (alloys, oxides, semiconductors, etc.) and layered thin-film structures.

We will present an overview XMCD and related techniques, with particular interest on the soft x-ray energy range (~ 100 - 2000 eV), where strong resonances at L2,3 edges of second-row transition metals and the M4,5 edges of rare earth elements lead to significant dichroic effects. Drawing on measurements conducted at the National Synchrotron Light Source and other synchrotrons, we will demonstrate the application of XMCD to studies of a range of FM materials, including oxide thin films, magnetic multilayers, and intriguing alloys with first order magneto-structural transitions. We will also discuss our development of a new technique, which combines ferromagnetic resonance with time-resolved XMCD, that utilizes the very short x-ray pulses produced by modern synchrotron sources.