Neutron diffraction studies of nanoparticle RMnO3 compounds (R=Pr, Nd)

The neutron diffraction measurements of the nano-size RMnO3 (R=Pr, Nd) manganites have been performed. The obtained results indicate that these compounds crystallize in the orthorhombic crystal structure described by the space group Pnma. Low temperature data indicate both the absence of a long-range magnetic order down to 1.5 K in the PrMnO3 sample annealed at 800 °C and the CxFy magnetic structure with a very low value of the Mn magnetic moment as compared with bulk sample in the sample annealed at 900 °C. In the NdMnO3 samples annealed at 850 °C and 900 °C the magnetic order is described by the CxFy mode in the Mn sublattice and the Fy mode in the Nd sublattice. The values of the Mn and Nd magnetic moments are lower that those in a bulk sample. Based on the model proposed in López-Quintela et al. [1] and Balcells et al. [2] the thickness of nonmagnetic shell was determined to be 7.1(4) nm in PrMnO3 and 4.6(5) nm in both the NdMnO3 compounds.