Abstract
The n=2 Ruddlesden–Popper phases LaSr 2CoMnO 7 and La 1.2Sr 1.8CoMnO 7 have been synthesized by a sol–gel method. The O6-type phases LaSr 2CoMnO 6 and La 1.2Sr 1.8CoMnO 6 were produced by reduction of the O7 phases under a hydrogen atmosphere. The materials crystallize in the tetragonal I4/ mmm space group with no evidence of long-range cation order in the neutron and electron diffraction data. Oxygen vacancies in the reduced materials are located primarily at the common apex of the double perovskite layers giving rise to square pyramidal coordination around cobalt and manganese ions. The oxidation states Co 3+/Mn 4+ and Co 2+/Mn 3+ predominate in the as-prepared and reduced materials, respectively. The materials are spin glasses at low temperature and the dominant magnetic interactions change from ferro- to antiferromagnetic following reduction.
Published Version
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