Magnetic circular x-ray dichroism in transverse geometry: Importance of noncollinear ground state moments

The orbital and spin magnetic moment and the magnetic dipole term of 3d transition metals are no longer collinear when the electron spins are forced out of the easy direction by an external magnetic field. This effect provides a simple way to measure with magnetic x-ray dichroism the anisotropy of the orbital magnetic moment and the magnetic dipole term in a geometry where the contribution of the spin magnetic moment disappears, i.e., with the photon helicity vector perpendicular to the magnetization direction.