Rare earth manganite nano-materials with giant magnetoresistance

This work presents results of researches on manganite with giant magnetoresistance. Studies on manganite are being significantly developed since few years. The manganite have been prepared by two processes using solar furnaces (especially useful when the melting point of the material is high): the vaporization-condensation in solar reactors leading to nano-phases and the splat-cooling from the melting point of the materials is high. The manganite has been prepared by this way and characterized by X-ray diffraction and High Resolution Electron Microscopy: the systems Nd-Sr-Mn-O: Nd2/3Sr1/3MnO3, [Nd0.767 Sr0.233]3.385 MnO3, [Nd2/3Sr1/3]4MnO3, [Nd2/3Sr1/3]5MnO3, the system La-Sr-Mn-O: [La2/3Sr1/3]4MnO3. The splat cooling method lead to nano-materials (stripes or rough powders depending on the viscosity of the melt material which can be amorphous or nano-structured. Nano-size powders can be obtained from that by ball milling. Bulk nano-materials can be prepared by sintering the powders. This method is especially well adapted to prepare (Nd or La)1-xSrxMnO3+/- nano-materials exhibiting giant magnetoresistance. The materials were analyzed by X-ray diffraction and high resolution electron microscopy. The vaporization - condensation method leads to chemical complex nano-crystals like manganite of lanthanum and strontium. The splat cooling method gives a better control for chemical composition of the materials. On the other hand the crystals are thicker than those obtained in the first method. (authors)