X-ray magnetic circular dichroism
X-ray dichroism is an umbrella term for several X-ray spectroscopic effects, which are based on the coupling of (X-ray ) photons at specific electron orbitals.
Circular magnetic X-ray dichroism
When circular magnetic X-ray (English X -ray magnetic circular dichroism and X- MCD), the absorption of X-rays by an atom with magnetic moment depends on whether the X-ray radiation is polarized left - or right-hand circular. Relevant is the difference spectrum between X-ray absorption spectrum of the left - or right - circularly polarized radiation. During the recording of polarized absorption spectra, the magnetization direction and the helicity of the X-ray photons is once again aligned parallel and anti- parallel. The absorption spectra obtained are subtracted from each other and from the difference of direct information on the specific element and the spin- orbital moment ( railway ) the moment of the valence band can be obtained by application of the so-called sum rules.
Typically, X -MCD studies of magnetic transition metals such as iron, cobalt and nickel, and their alloys or compounds, including now also metal complexes is carried out. Here, X-ray absorption spectra are measured at the 2p absorption edge. Here, find transitions occur in the 3d shell, which can be magnetically strong, so are magnetic field dependent.
Linear magnetic X-ray dichroism
Linear magnetic X-ray dichroism is the circular dichroism similar magneto- optical effect, but of a higher order (quadratic in the spin- torque M ) and thus weaker. This form of magnetic X-ray dichroism is useful to obtain magnetic information, eg of antiferromagnets, which have no circular X-ray dichroism.
Linear ( non-magnetic ) X-ray dichroism
Linear ( non-magnetic ) X-ray dichroism is a sequence of non- crystalline anisotropy of magnetic origin and is often difficult to separate from the linear magnetic X-ray.
The X-ray emission has circular and linear dichroism, which is, however, difficult to interpret, since no sum rules could be set up.
In the photoelectron emission angle the distribution is a function of the helicity of the exciting X-ray radiation and it is known based on the X -MCD effect as dichroism.