Crystal growth, structure and magnetic properties of Ca10Cr7O28
  A detailed diffraction study of Ca10Cr7O28 is presented which adds significant new insights into the structural and magnetic properties of this compound. A new crystal structure type was used where the a and b axes are doubled compared to previous models providing a more plausible structure where all crystallographic sites are fully occupied. The presence of two different valences of chromium was verified and the locations of the magnetic Cr5+ and non-magnetic Cr6+ ions were identified. The Cr5+ ions have spin-1/2 and form distorted kagome bilayers which are stacked in an ABC arrangement along the c axis. These results lay the foundation for understanding of the quantum spin liquid behavior in Ca10Cr7O28 which has recently been reported in [C. Balz et al., Nature Physics, 12, 942 (2016)]. 
Christian Balz, Bella Lake, Manfred Reehuis, A. T. M. Nazmul Islam,   Yogesh Singh, Oleksandr Prokhnenko, Philip Pattison, S...
cond-mat.str-el