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The size effects on the charge ordering (CO) and magnetic properties in La(0.25)Ca(0.75)MnO(3) with mean particle size ranging from 40 to 2000 nm were studied. With decreasing particle size the CO transition temperature shifts to lower temperature and the transition width becomes increasingly wide, indicating the weakening of the CO state. Meanwhile the ferromagnetic (FM) cluster glass state appears and the magnetization at low temperature increases significantly. The behaviour is due to the increasing uncompensated surface spins which weaken the antiferromagnetic interaction and disfavour the formation of the CO state. The suppression of the CO state and appearance of the FM cluster glass state are also found in La(0.25)Ca(0.75)MnO(3) nanowires fabricated by a sol-gel template method. These results indicate that the CO state can be modulated effectively by varying particle size, which has an important implication for nano-device applications of manganites. (c) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.