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

Abstract

The longitudinal and transverse ultrasonic velocities and attenuations, the transport and magnetic properties, as well as the structural changes of polycrystalline La0.25Ca0.75Mn0.93Cr0.07O3 have been studied systematically. A velocity minimum and an attenuation peak for both longitudinal and transverse waves occur around the temperature Tco of charge ordering transition accompanied by the structural change from a cubic to a tetragonal phase. Near temperature TN (where the c-axis length shows a maximum), the sharp decrease of velocities for both waves and the appearance of a longitudinal attenuation peak are attributed to the antiferromagnetic transition together with the anomalous change in c-axis length of the tetragonal phase. The simultaneous occurrence of the ultrasonic, lattice, charge ordering, magnetic, and transport anomalous characteristics indicates the strong electron–phonon and spin–phonon interactions in the system.