Anion Vacancy Distribution and Magnetism in the New Reduced Layered Co(II)/Co(I) Phase LaSrCoO_3.5-x

The new reduced K 2 NiF 4 Co(II) phase, LaSrCoO 3.5 - x, is prepared by reduction of the Co(III) containing LaSrCoO 4 using H 2 gas and the new hydride solid−solid reduction methods. The hydride route is superior in both crystallinity and control of phase purity and allows access to reduced phases containing substantial concentrations of Co(I). The anion vacancies are located within the MO 2 planes of the K 2 NiF 4 structure but do not prevent the onset of long-range antiferromagnetic order: the magnetic structure is refined using a noncollinear model consistent with the tetragonal crystal symmetry.