Intergranular magnetoresistance in nanomanganites

摘要

In this paper we present some of the most important magnetic and transport properties of mixed-valence manganite nanoparticles. The samples were prepared by a sol-gel method, which allows us to control particle size and, in this way, to obtain new properties of the archetypal ferromagnetic-metallic compound La_(2/3)Ca_(1/3)MnO_3. Magnetic properties allow us to present a model for the nanoparticles based on an ideal inner core and an outer shell in which the magnetism is modified by oxygen non-stoichiometry, vacancies and stress. The experimental results obtained from the electrical transport properties, namely increasing intergranular magnetoresistance (MR) with reducing particle size, tuning of intrinsic colossal MR and low-temperature electrostatic blocking effects, seem to support the proposed model.