Magnetic and Magnetotransport Properties of ${\rm La}_{0.7}{\rm Sr}_{0.2}{\rm Ca}_{0.1}{\rm MnO}_{3}$ Prepared From Nanoparticles

We have studied magnetic and magnetotransport properties of a polycrystalline ceramics of La_0.7Sr_0.2Ca_0.1MnO₃ (LSCM) prepared from nanoparticles. The Curie temperature (T_C) of the sample is about 340 K. Basing on the magnetic-field dependences of magnetization measured around T_C, maximum magnetic-entropy changes under the applied fields of 10, 20 and 30 kOe are about 1.73, 2.74, 3.52 J/kg.K, respectively, which are higher than those reported on a parent compound of La_0.7Sr_0.3MnO₃. To understand magnetic-interaction mechanisms taking place in the system, the critical behavior has been taken into account. By using the modified Arrott plot method, β and γ values associated with the spontaneous magnetization (M_s) and inverse initial susceptibility (χ₀^-1) have been obtained to be 0.472 ± 0.016 and 1.061 ± 0.024, respectively. These critical parameters are close to those expected for the mean-field theory (with β = 0.5 , and γ = 1.0 ). A small deviation in value between our results and those expected for the mean-field theory could be due to an inhomogeneity in magnetism and/or interaction competitions between antiferromagnetic pairs ( Mn³⁺-Mn³⁺ and Mn⁴⁺-Mn⁴⁺ ) and a ferromagnetic pair of Mn³⁺-Mn⁴⁺ in LSCM. Interestingly, in the temperature range of 180-300 K, magnetoresistance values keep quite stable at about 16 and 27% for the magnetic fields of 1 and 7 kOe, respectively. This makes LSCM more suitable to applications of magnetic sensitive sensors and reading heads working in a large temperature range.