Ultrasonic study on charge ordering, magnetic, and structural changes in La0.25Ca0.75Mn0.93Cr0.07O3

The longitudinal and transverse ultrasonic velocities and attenuations, the transport and magnetic properties, as well as the structural changes of po lycrystalline La0.25Ca0.75Mn0.93Cr0.07O3 have been studied systematically. A velocity minimum and an attenuation peak for both longitudinal and transv erse waves occur around the temperature T-co of charge ordering transition accompanied by the structural change from a cubic to a tetragonal phase. Ne ar temperature T-N (where the c-axis length shows a maximum), the sharp dec rease of velocities for both waves and the appearance of a longitudinal att enuation peak are attributed to the antiferromagnetic transition together w ith the anomalous change in c-axis length of the tetragonal phase. The simu ltaneous occurrence of the ultrasonic, lattice, charge ordering, magnetic, and transport anomalous characteristics indicates the strong electron-phono n and spin-phonon interactions in the system. (C) 2000 American Institute o f Physics. [S0003-6951(00)01309-7].