Abstract
The longitudinal and transverse ultrasonic sound velocity and attenuation, as well as electric resistance have been carefully measured in single-phase polycrystalline giant magnetoresistance perovskite La 0.67Sr 0.3Mn 0.87Fe 0.13O 3 at a frequency of 10 MHz, from 20 to 300 K. A big electric resistance peak was observed at 85 K ( T C). At the temperature above T C, the resistivity can be fitted well by Mott’s law ρ=exp ( T 0/ T) 1/4 and both the longitudinal and transverse sound velocities show a lattice softening, which was accompanied by an attenuation peak. This simultaneous occurrence of electron and lattice softening implies electron–phonon coupling, known to exist for the octahedrally coordinated d 4 ion, originating in the Jahn–Teller distortion. Below 55 K, pronounced sound-velocity softening for both longitudinal and transverse waves was observed; this may correspond to the formation of a spin-glass state.
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