Structural characterization and properties of the perovskite (NaLa)(MW)O6(M=Co, Ni): two new members in the group–subgroup relations for the perovskite-type structures

Abstract

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) Å, β=89.99(3)°; M=Ni: a=5.517(5), b=5.518(7), c=7.862(2) Å, β=90.02(4)°; space group P2 ₁ /m]. The structure consists of an ordered arrangement of MO ₆ and WO ₆ 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.