Light orbital magnetic moments

The magnetic moments of the heavy RE elements (Gd, Tb, Dy, etc) are coupled antiparallel to the magnetic moments of the TM elements (Fe, Co, etc). The REj TM alloys are therefore ferrimagnetic below their Curie temperature (T )- The heavy TM moments form one magnetic sublattice and the RE moments the other one. In contrast, the light RE moments (eg, Nd, Pr) couple parallel to the moments of TM. The RE spia is always antiparallel to the TM spia, but for the light RE elements, the orbital momentum is coupled antiparallel to the spia and larger than the spia. 

Since the -factor associated with orbital angular momentum has a value of 1 if 5 = 0, the factor does not always have to be included. The value for the z-component of the magnetic moment aligned with the axis of light propagation is defined as... 

Triplet states are generally molecules in which one electron is promoted to a higher electronic orbital (e.g. by the absorption of light) under spin reversal, i.e. it is no longer paired with its partner in the orbital it has left and the two electrons have a combined magnetic moment what is twice that of a radical. Some molecules, e.g. dioxygen, have a triplet ground state. 

Fig. 8. Electronic band structure of spin polarized fee Ni obtained by assuming a reduced velocity of light, c = 68.5 a.u., in the RFPLO method. The magnetic moment points along (001). All symmetry-determined degeneracies are lifted by spin-orbit interaction.

From the experimentally determined paramagnetic susceptibility, one can calculate the magnetic moments of the transition metal ions in the system. If the magnetic moment is known, it is simple to calculate the number of unpaired electrons. This throws light on the oxidation number of the metal ion being examined or the central atom of the complex, and also on its low- or high-spin electronic structure. Further, if the number of unpaired electrons in the complex is known, the value of the orbital momentum contribution can be calculated in certain cases this permits conclusions to be drawn about the symmetry of the complex (solvate) (see, e.g., ref. [Bu 73]). 

Concerning induced orbital moments of U-based intermetallic compounds, many PND experiments have been performed and have shown that the ratio iL/ -is can be used as a measure of the hybridisation [42-44] (in the light actinides, orbital and spin moments are oppositely directed and the neutron magnetic form factors are highly sensitive to the ratio uL/us). Indeed, this ratio is reduced as compared to the free ion expectations (Figure 4). 

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