Structural and magnetic characterization of the double perovskites R2NiRuO6 (RÂ =Â Pr-Er): A neutron diffraction study

Novel members of the R2NiRuO6 family of double perovskites have been prepared via a nitrate-citrate route, followed by annealing treatments in air in the 1100-1300 °C temperature range. The crystal and magnetic structures were characterized from neutron powder diffraction (NPD) data at 300 K and 2 K. All the samples are monoclinic, P21/n space group, with a √2a0×√2a0×2a0 unit-cell, compared to the simple perovskite a0 edge. Ni2+ and Ru4+ ions occupy distinct octahedral positions, with a certain antisite disordering. The magnetic structures are defined by the propagation vector k = 0. The magnetic moments of the Ni2+ cations are antiparallel to the spins of the Ru4+ sublattice; the structure can be described as ferromagnetic [011] layers antiferromagnetically (AFM) coupled to each other. For R = Ho and Er perovskites, the rare-earth moments participate in the magnetic structure: Ho3+ cations are ordered along the direction (010) in alternate planes AFM coupled and the magnetic moments of Er3+ are ferromagnetically ordered along the c axis.

The establishment of charge ordering between Ni2+ and Ru4+ ions dramatically changes the physical properties of the parent perovskites RNiO3.286