Nuclear and magnetic order in Y(Ni,Mn)O3 manganites by neutron powder diffraction

Neutron powder diffraction experiments performed on two selected compositions of the yttrium-based solid solution YNixMn1−xO3 (x=0.25 and 0.50), clearly reveal a nuclear order between the Ni2+ and Mn4+ ions in the half-substituted compound YNi0.50Mn0.50O3, so that the crystal structure is no longer described in the conventional orthorhombic Pbnm space group, but in the monoclinic P21/n, all over the investigated temperature range (1.5–300 K). However, both X-rays diagrams and neutron patterns of the YNi0.25Mn0.75O3 phase are indexed in the Pbnm orthorhombic-like symmetry, indicating that the Mn and Ni ions are randomly distributed on the octahedral sites. ition, neutron diffraction points out that the nature of the magnetic ordering is strongly connected to the structural properties. Whereas no long-range 3D-magnetic ordering was detected for the Pbnm YNi0.25Mn0.75O3 phase, the YNi0.50Mn0.50O3 compound exhibits a magnetic transition at TC∼85 K. The magnetic structure consists of two collinear Mn4+ and Ni2+ ferromagnetic layers (Fx0Fz magnetic configurations) with saturated magnetic moment values of 2.25(2) and 1.57(2) μB for Mn4+ and Ni2+, respectively, at 1.5 K.