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Pr0.57Ca0.43MnO3 nanoparticles with an average particle size of similar to 20 nm have been synthesized using hydrothermal method in combination with post-annealing, and characterized using X-ray diffraction, X-ray photoelectron spectrometer, high-resolution transmission electron microscopy and superconducting quantum interference device magnetometery. The results show that the hydrothermal synthesis of Pr1-xCaxMnO3 compound below 240 degrees C is difficult. The Pr0.57Ca0.43MnO3 nanoparticles obtained by annealing the hydrothermal products at 900 degrees C for 2 h present an orthorhombic perovskite structure with the same lattice as bulk Pr0.6Sr0.4MnO3. Magnetic characterization reveals that the low-temperature antiferromagnetic and charge ordering transitions identified in bulk Pr0.57Ca0.43MnO3 are completely suppressed in the nanoparticles, while a ferromagnetic transition occurs at -110 K. The spin-freezing behavior at low temperature for the Pr0.57Ca0.43MnO3 nanoparticles is demonstrated. (c) 2006 Elsevier B.V. All rights reserved.