Inhomogeneous magnetism studied by ESR in La1-xSrxMnO3 (0.45 <= x <= 0.62)

摘要

The influence of strontium substitution on lanthanum site in La1-xSrxMnO3 manganites has been investigated with x ranging from 0.55 to 0.62 in the 130-400 K temperature range. Powder X-ray diffraction reveals structural changes from rhomboedral to tetragonal and to orthorhombic structures upon increasing Sr substitution. Magnetic properties also show a rich variety of phases and behaviors, including coexistence of phases above Curie temperature. The electron spin resonance measurements allow quantifying paramagnetic phases and properties with randomly distributed spins and ferromagnetic phases or inclusions with oriented spins giving rise to a local magnetic field. When x = 0.55, 0.57, the ferromagnetic state is the minor phase embedded in a paramagnetic matrix. Conversely, when x increases, the ferromagnetic phase grows and becomes the only phase observed for x = 0.62. (C) 2017 Elsevier Masson SAS. All rights reserved.