Anomalous Lattice Distortion in Pr-Substituted Double-Layered Perovskite Manganite La_(1.2)Sr_(1.8)Mn_2O_7 Single Crystals: II

摘要

Thermal expansion and magnetostriction both in the ab-plane and along the c-axis of double-layered perovskite manganite (La_(1-z)Pr_z)_(1.2)Sr_(1.8)Mn_2O_7 (z = 0, 0.2, 0.4 and 0.6) single crystals have been measured as a function of temperature and magnetic field. The anomalous lattice distortion and the giant magnetostriction associated with the CMR were observed near the PI to FM transition temperature T_c. These findings indicate that the PI to FM transition and the CMR near T_c are not associated with the anisotropic lattice striction concerning the static John-Teller effect but with the negative volume striction related to the delocalization of polarons to itinerant carriers.