Interplay Between Structural, Jahn–Teller, and Magnetic States of Slightly Doped Lanthanum Manganites

Abstract

By combining the results of elastic moduli, electrical resistivity, and magnetization measurements for La$_{1-x}$Sr$_{x}$MnO$_{3}$ (x = 0.125, x = 0.15, and x = 0.175), we have constructed a phase diagram that describes the structural, magnetic, transport properties and the relationships among them as a function of the composition and temperature (140–340 K). The local, intermediate, and cooperative Jahn–Teller distortions of the octahedral structural units MnO$_{6}$ have been studied. It is common for these distortions to be observed using probes of intermediate structures (domains or super-cells), but they are absent in the averaged crystallographic structure. In the cooperative Jahn–Teller distorted phase, the macroscopic sample length is temperature dependent. We presume that the structural transitions from the cooperative Jahn–Teller phase to the charge ordering phase at low temperatures (150 and 180 K at x = 0.125 and x = 0.15) are due to the increase in the spontaneous magnetization with the conservation of the local deformations of separate octahedra. The agreement between the types of the orbital ordering and the local, intermediate, and Jahn–Teller cooperative distortions of octahedra was established.