Direct exchange interaction

The I—H theory also treats the time dependence of fluorescence in the direct exchange interaction. This is expressed in Eq. (5) above. 

It was shown in section 3 that the transport properties of magnetic R-non-transition metal compounds can be understood in terms of a direct exchange interaction between conduction electrons and R localized moments. This interaction leads to an indirect RKKY interaction between the localized moments which describes the magnetic properties of these compounds. 

The five d orbitals of a transition metal atom B are degenerate however, with more than one electron in the d manifold, the spin degeneracy is removed by the ferromagnetic direct-exchange interaction between electron spins in atomic orthogonal orbitals. Transition metal B cations usually introduce filled and/or empty d states within the gap between the anion p bands and lanthanide 5d bands, which lowers the probability that the lanthanide ion can have two valence states in a transition metal perovsldte. 

Anderson further discusses the direct exchange interaction between d electrons and an indirect exchange interaction through the spin polarization. 

It must be said that the idea of a correlation between mobile and localized electrons appeared in the thirties of the last century and it was proposed by two soviet scientists Schubin and Vonsovsky in the paper [28]. In this model it is supposed that the localized electrons (d-electrons) are in magnetic order due to, for example, direct exchange interaction, while conduction electrons (s-electrons) are magnetized due to s-d interaction, which leads to a number of peculiarities in the behavior of the last. A detailed description of this model and the various effects that appear when it is used can be foimd in the monograph [29]. 

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