Structural and Magnetocaloric Properties of Classical Rare-Earth Manganite Ceramics

Structure, microstructure, chemical and phase composition, as well as magnetic state and magnetocaloric effect of the
$\text{La}_{0.9}\text{Mn}_{1.1}\mathrm{O}_{3}$
manganite have been investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and magnetic methods. The
$\text{La}_{0.9}\text{Mn}_{1.1}\mathrm{O}_{3}$
ceramics have been synthesized using a two-step solid-state reaction method at an annealing temperature of
$1150^{\circ}\mathrm{C}$
(22 h). Based on the X-ray diffraction results, a crystal structure of the
$\text{La}_{0.9}\text{Mn}_{1.1}\mathrm{O}_{3}$
ceramic has a rhombohedral
$R-3c$
(No. 167) type of symmetry. Chemical and phase composition of the
$\text{La}_{0.9}\text{Mn}_{1.1}\mathrm{O}_{3}$
sample has been confirmed by energy-dispersive X-ray spectroscopy. The average grain size has been determined by means of Nano Measure 1.2.5 software and is 1.6
$\mu \mathrm{m}$
. Based on the magnetic data,
$\text{La}_{0.9}\text{Mn}_{1.1}\mathrm{O}_{3}$
ceramic displays a ferromagnetic to paramagnetic phase transition at the Curie temperature
$T_{\mathrm{C}}=227\mathrm{K}$
with a high magnetic entropy change
$\Delta S_{\mathrm{M}}{}^{\max}=-3.50\mathrm{J}/(\text{kg}\cdot \mathrm{K})$
at the field of 2 T. Moreover, the magnetic parameters in the paramagnetic state have been defined using the Curie- Weiss law.