Transport and ultrasonic properties in La0.67Sr0.33Mn0.87Fe0.13O3 perovskite

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 La0.67Sr0.3Mn0.87Fe0.13O3 at a frequency of 10 MHz, from 20 to 300 K. A big electric resistance peak was observed at 85 K (TC). At the temperature above TC, the resistivity can be fitted well by Mottʹs law rho=exp (T0/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 d4 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.