Magnetic properties of nanoparticle La0.7Ca0.3MnO3 under applied hydrostatic pressure

Abstract

Pressure effects on magnetic properties of two La0.7Ca0.3MnO3 nanoparticle samples with different mean particle sizes were investigated. Both the samples were prepared by the glycine-nitrate method: sample S-as-prepared (10 nm), and sample S-900-subsequently annealed at 900 A degrees C for 2 h (50 nm). Magnetization measurements revealed remarkable differences in magnetic properties with the applied pressure up to 0.75 GPa: (i) for S sample, both transition temperatures, para-to-ferromagnetic T (C) = 120 K and spin-glass-like transition T (f) = 102 K, decrease with the pressure with the respective pressure coefficients dT (C)/dP = -2.9 K/GPa and dT (f)/dP = -4.4 K/GPa; (ii) for S-900 sample, para-to-ferromagnetic transition temperature T (C) = 261 K increases with pressure with the pressure coefficient dT (C)/dP = 14.8 K/GPa. At the same time, saturation magnetization M (S) recorded at 10 K decreases/increases with pressure for S/S-900 sample, respectively. Explanation of these unusual pressure effects on the magnetism of sample S is proposed within the scenario of the combined contributions of two types of disorders present in the system: surface disorder introduced by the particle shell, and structural disorder of the particle core caused by the prominent Jahn-Teller distortion. Both disorders tend to vanish with the annealing of the system (i.e., with the nanoparticle growth), and so the behavior of the sample S-900 is similar to that previously observed for the bulk counterpart.