  In this paper we present the results of the synthesis and characterisation of
nanocrystalline La1-xNaxMnO3+delta samples. Two synthetic routes were employed:
polyacrylamide-based sol-gel and propellant synthesis. Pure, single phase
materials were obtained with grain size around 35 nm for the sol-gel samples
and around 55 nm for the propellant ones, which moreover present a more broaden
grain size distribution. For both series a superparamagnetic behaviour was
evidenced by means of magnetisation and EPR measurements with peculiar features
ascribable to the different grain sizes and morphology. Preliminary
magnetoresistivity measurements show enhanced low-field (< 1 T)
magnetoresistance values which suggest an interesting applicative use of these
manganites.
