Synthesis, structure, and magnetic properties of Ca3BMnO6 (B= Ni, Zn) and Ca3ZnCoO6 crystallizing in the K4CdCl6 structure

Ca3BMnO6 (B = Ni, Zn) and Ca3ZnCoO6 were synthesized and studied by X-ray powder diffraction, neutron powder diffraction, and SQUID magnetometry. All these compounds were found to crystallize in the K4CdCl6 structure containing alternate chains made of face-sharing B(II)O-6 trigonal prisms and B'(IV)O-6 octahedra (B' = Mn, Co). Ca3NiMnO6(CNMO) and Ca3ZnMnO6 (CZMO) were found to be antiferromagnets with a T-N of 19 and 25.5 K, respectively. CNMO showed a pronounced one-dimensional antiferromagnetic character like a broad susceptibility maximum at 100 K due to short range ordering, while CZMO behaved as a three-dimensional system since the presence of nonmagnetic Zn2+ ions suppressed the intrachain exchange interaction. A simple collinear antiferromagnetic structure with an ordered moment of 2.33(15) mu(B)/Mn was found in CZMO, while CNMO showed a spiral structure with ordered moments of 2.2(2) mu(B)/Mn and 1.4(2) mu(B)/Ni. Ca3ZnCoO6, on the other hand, showed a ferromagnetic, nonlinear field dependence of magnetization below 90 K, with a hysteresis appearing just below 25 K, and a spontaneous moment measured at 5 K was 0.6 mu(B)/Co, suggesting the Co4+ ions being in low spin state. (C) 1999 Academic Press.