Optical-spectroscopic detection of spin-exchange interaction pyrochlore molybdates.
Optical spectroscopy was used to determine nearest-neighbor spin correlations in pyrochlore molybdates R2Mo2O7 (R=Y, Sm, and Nd), which exhibit ferromagnetic metal to spin-glass insulator transition as the R ion size decreases. Using an analysis based on the orbitally degenerate Hubbard model, we could estimate important physical parameters, such as the effective on-site Coulomb energy U(eff) and the Hund rule exchange coupling J(H). We demonstrated experimentally and theoretically that the effective superexchange interaction between the Mo ions depends on J(H)/U(eff), which determines the phase boundary of the magnetic ground states.
Kim
M W
MW
ReCOE & School of Physics, Seoul National University, Seoul 151-747, Korea.
Lee
Y S
YS
Noh
T W
TW
Yu
Jaejun
J
Moritomo
Y
Y