Phase segregation in the hole-doped manganite Nd0.93MriO2.96:: magnetic measurements and neutron diffraction

Lactmar-controlled Nd0.93MnO2.96 orthorhombic perovskite prepared at 1200degreesC has been studied at low temperature. Magnetization measurements suggest the coexistence below 80 K of ferro- and antiferromagnetic interactions between Mn atoms as in the stoichiometric parent compound NdMnO3. Nevertheless, spontaneous magnetization curves obtained after sample cooling under a magnetic field of 500 Oe (FC) and without magnetic field (ZFC) reveal a much original behavior. Magnetization changes sign twice on ZFC curve; strong negative magnetization is observed below 19 K on FC curve. On the basis of neutron diffraction data, this behavior is interpreted by considering the coexistence of two perovskite phases having chemical compositions and magnetic ordering temperatures slightly different; ferromagnetic components in the clusters of both phases are antiferromagnetically coupled in the range 20-80 K. Ferromagnetic ordering at 19 K of Nd atoms is accompanied by a rearrangement of the Mn ferromagnetic components which become parallel in all the clusters. (C) 2004 Elsevier B.V. All rights reserved.