(CaMn)MnTeO - An Anomalously Stable High-Pressure Double Perovskite.

High pressure high temperature treatments of the composition CaMnMnTeO are found to yield only an ABB'O-type double perovskite (CaMn)MnTeO, rather than a AA'BB'O double double perovskite with A- and B- site cation order as found in analogs CaMnMnReO and CaMnMnWO with similar cation sizes. Double perovskite (CaMn)MnTeO adopts a monoclinic structure in space group P2/n with a framework of highly tilted MnO and TeO octahedra enclosing disordered Ca and Mn cations. Magnetic measurements show that (CaMn)MnTeO is a highly frustrated spin glass with a freezing transition at 5 K, and no long-range spin order is apparent by neutron diffraction at 1.6 K.