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1 Advanced Nano Technologies, 112 Radium Street, Welshpool, WA 6106, Australia
2 Department of Physics, The University of Western Australia,
35 Stirling Highway, Crawley, WA
| Nanoparticles of La0.7Ca0.3MnO3 have been synthesised via the chemical reaction 0.7LaCl3 + 0.3CaCl2 + MnCl2 + 2.35Na2CO3 + 0.325O2 --> La0.7Ca0.3MnO3 + 4.7NaCl + 2.35CO2 effected by high-energy ball milling and subsequent heat treatment. Single-phase La0.7Ca0.3MnO3 particles having crystallite sizes ranging between 24 nm and 1 µm were obtained after removing the NaCl by-product phase by washing. Magnetic measurements showed that the spontaneous magnetisation decreased with deceasing crystallite size; that the coercivity increased with decreasing temperature; and that below about 50 K field-cooled hysteresis loops for the smallest particles were shifted towards the negative field. These observations are discussed in terms of a model in which it is assumed that each crystallite consists of a ferromagnetic core and a spin-glass shell that are exchange-coupled. |
full paper (pdf, 256 Kb)