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.
X-ray absorption
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.
X-ray emission
The X-ray emission has circular and linear dichroism, which is, however, difficult to interpret, since no sum rules could be set up.
Photoelectron emission
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.