Pb. Zhao et al., A POSSIBLE MECHANISM FOR QUASI-2-DIMENSIONAL FERROMAGNETISM - THE SPECTRUM GAP INDUCED BY S-D EXCHANGE INTERACTION, Journal of physics. Condensed matter, 8(23), 1996, pp. 4157-4163
A quasi-two-dimensional magnetic system is studied in which magnetic a
toms are confined in the two-dimensional plane but the conduction elec
trons are in fact three-dimensional. By virtue of spin-wave theory, we
find that a spectrum gap can be formed at the bottom of the spin-wave
spectrum, induced by the s-d exchange interaction between conduction
electrons and magnetic localized electrons. Thus, a new possible mecha
nism is proposed for two-dimensional ferromagnetic order at finite tem
perature.