Magnetic Circular Dichroism (MCD) Experiment
What is the origin of magnetism? Circularly polarized SR plays a key role
in the study of magnetic materials. Much valuable information on
the origin of magnetism can be obtained from MCD studies.
Studies involving transition and rare earth metals have been
performed with spectroscopic methods.
(a) Illustration of MCD in the 2p-3d excitation.
In the presence of the applied magnetic field H, there are some empty
down spin 3d states. In this case only the 2p electrons with down spin
can be excited into the 3d states because of the conservation of spins.
When the orbital motion of the 2p states is in the same direction
as the circular motion of the incident light the transition probability
is larger, while when the two motions are in opposite directions
the probability is small. As a result the spectrum shown in
the figure (b) is obtained as the difference in the absorption
of right- and left- circularly polarized light (LCP and RCP).
(c)Experimental MCD spectrum of 2p-3d excitation of Ni,
which corresponds to the expected spectrum (b). The difference
in the integrated values between the L3 and L2
edges suggests
the contribution of 3d electrons to the magnetic moment.
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