[en] Full text: Following the general growing interest to explore the influence of confinement effects on physical phenomena on nanoscale, research efforts on nanostructured systems are rapidly emerging, by virtue of their technological application in branches as telecommunication, medicine and biotechnology. Among the several candidate materials, the manganites can present interesting properties as magnetoresistance, magnetostriction and magnetocaloric effect. The manganites are manganese oxides that belong to the family of crystalline ceramics with perovskite structure, AMnO₃ , where A represents trivalent cations (rare earths) and / or bivalents (alkaline earth metals). For lanthanum (La) based manganites, the chemical doping of the site A with alkaline earth metals such as calcium (Ca) and strontium (Sr) allow one to tune the temperature of the magnetic phase transitions. Besides,the nature of the magnetic phase transitions (first/second order) can be related to the grain size, depending on the surface to volume ratio. The aim of this work is to investigate physical properties of magnetic nanoparticles of La_0,67Ca_0,33MnO₃ , synthetized via sol-gel method. The samples were heat treated at different temperatures between 600 and 1000 ° C. They were structurally characterized by X-ray diffraction and it was observed high crystallinity, with peaks corresponding to the desired perovskite phase. Magnetization and electron spin resonance (ESR) were used to magnetically characterize the samples. Magnetization measurements show a ferromagnetic ordering and a second order phase transition around 260 K. ESR spectra were obtained, with the resonant field and peak-to-peak width presenting temperature dependence, also revealing the magnetic phase transition. (author)