Microscopic spin interactions in the CMR manganites

Fernandez-Baca, J. A.; Dai, Pengcheng; Kawano-Furukawa, H.; Yoshizawa, H.; Plummer, E. W.; Katano, S.; Tomioka, Y.; Tokura, Y.

Microscopic spin interactions in the CMR manganites

Authors

Fernandez-Baca, J. A.

Description

Using inelastic neutron scattering we measured the microscopic magnetic coupling associated with the ferromagnetic (FM) clusters of the ``colossal magnetoresistance'' (CMR) compound Pr$_{0.70}$Ca$_{0.30}$MnO$_3$. When the insulating to metal (I-M) transition is induced by an external magnetic field there is a discontinuous change in the spin-wave stiffness constant. This result indicates that the probed regions undergo a first-order transition from an insulating to a metallic state, and that there are no FM metallic domains in the insulating region. We argue that the I-M transition in the CMR manganites is more complex than the simple percolation of large FM metallic clusters.
4 pages, 4 figures