Evolution of spin-wave excitations in ferromagnetic metallic manganites.
Neutron scattering results are presented for spin-wave excitations of three ferromagnetic metallic A1-xA'xMnO3 manganites (where A and A' are rare- and alkaline-earth-metal ions), which when combined with previous work elucidate the systematics of the interactions as a function of carrier concentration x, on-site disorder, and strength of the lattice distortion. The long-wavelength spin dynamics show only a very weak dependence across the series. The ratio of fourth to first neighbor exchange (J4/J1) that controls the zone boundary magnon softening changes systematically with x, but does not depend on the other parameters. None of the prevailing models can account for these behaviors.
Ye
F
F
Center for Neutron Scattering, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA.
Dai
Pengcheng
P
Fernandez-Baca
J A
JA
Sha
Hao
H
Lynn
J W
JW
Kawano-Furukawa
H
H
Tomioka
Y
Y
Tokura
Y
Y
Zhang
Jiandi
J