Structural characterization and properties of the perovskite (NaLa)(MW)O-6 (M=Co, Ni): Two new members in the group-subgroup relations for the perovskite-type structures

The crystal structures of (NaLa)(MW)O-6 (M = Co, Ni) suggest that both adopt a monoclinic perovskite-type structure [M = Co: a = 5.546(3), b = 5.545(4), c = 7.903(6) Angstrom, beta = 89.99(3)degrees; M = Ni: a = 5.517(5), b = 5.518(7), c = 7.862(2) Angstrom, beta = 90.02(4)degrees; space group P2(1)/m]. The structure consists of an ordered arrangement of MO6 and WO6 octahedra (in B sites) which share corners and alternate planes of La and Na cations along the c-axis (in A sites). This structure is analysed on the basis of a general group subgroup symmetry relationship for some perovskites that were previously described, and the electronic and magnetic properties of both compounds are discussed.