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

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 S900—subsequently annealed at 900 °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 TC = 120 K and spin-glass-like transition Tf = 102 K, decrease with the pressure with the respective pressure coefficients dTC/dP = −2.9 K/GPa and dTf/dP = −4.4 K/GPa; (ii) for S900 sample, para-to-ferromagnetic transition temperature TC = 261 K increases with pressure with the pressure coefficient dTC/dP = 14.8 K/GPa. At the same time, saturation magnetization MS recorded at 10 K decreases/increases with pressure for S/S900 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 S900 is similar to that previously observed for the bulk counterpart.