Strong magnetic circular dichroism at the M2,3 edges in ferromagnetic Ni and ferrimagnetic Fe3O4

Abstract

Magnetic-circular-dichroism (MCD) spectra have been obtained at and around the ${\mathit{M}}_{2,3}$ core absorption edges in single crystals of ferromagnetic Ni and ferrimagnetic ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$. Furthermore, strong MCD signals were observed for the weak multiplet structures of ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$ in the prethreshold region. The experiments were performed using a bulk-sensitive reflection method by utilizing directly characterized, circularly polarized synchrotron radiation in conjunction with an ultrahigh-vacuum-compatible, i.e., bakable, superconducting magnet of interesting design. The present observation of a strong MCD not only provides a sensitive method for probing the local magnetic states of magnetic substances, but also could provide valuable information concerning the 3d electronic states of these materials.