Thermodynamics transport and magnetic properties of nanostructured compounds can be quite different from that of bulk materials. In our recent works, the relation between the magnetic properties and the nanosize of Ce0.8Gd0.2O1.9 samples have been investigated. It will be shown that nanostructured Ce0.8Gd0.2O1.9 samples shows superparamagnetic behaviour. The extent of the inner field Ha is a function of the particle dimension (see Fig.1).

Figure 1: Left particle size distribution P(D) obtained throughout Warren-Averbach analysis for Ce_0.8Gd_0.2O_1.9 nanocrystals; right internal field Ha as a function of particle diameter (DV) for the same composition.

The local structure of Ce_1-xGd_xO_2-x/2 samples has been investigated by means of PDF analysis. In Fig. 2 the G(r) function of a microstructured Ce_0.8Gd_0.2O_1.9 sample (black) is shown as well as the G(r) function relative to two nanostructured phases of the same compound. The G(r) amplitude of the nanostructured samples decreases rapidly at high r values due to the limited particle size.

Figure 2: G(r) function relative to Ce_0.8Gd_0.2O_1.9 samples in the 1.5 < r < 10 Å and 90 < r < 100 Å regions. Black = microstructured; blue = sol-gel nanosample annealed at 700 °C; red = sol-gel nanosample annealed at 500 °C.

The local distortions introduced by Gd doping and nanosize structure of Ce_1-xGd_xO_2-x/2 samples will be discussed.

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