Infrared observation of the Hund's mechanism in an electron-doped manganite

In the midinfrared absorption of Sr1-xCexMnO3 at low electron doping (x=0.05), a band at 0.3 eV is fully replaced by another one at 0.9 eV as the system becomes antiferromagnetic (AF) of type G. A weaker effect occurs at x=0.10 for an AF phase of type C. One thus directly measures the electron hopping energies for spin parallel and antiparallel to that of the host ion. The Hund's, crystal-field, and Jahn-Teller splittings for the Mn3+ ions in a Mn4+ matrix can also be derived.