Published online by Cambridge University Press: 16 February 2011
Powder neutron diffraction and magnetization measurements are presented on the Co2Ru1-xMnxO4 system. In these materials the tetrahedral (A) sites are occupied by Co2+ (S = 3/2) ions, and the octahedral (B) sites are jointly occupied by Co3+ (low spin, S = 0), Ru3+ (low spin, S = 1/2), and Mn3+ (S = 2) ions. The measurements reveal that Co2RuO4 undergoes a spin-glass transition, Co2MnO4 is a collinear ferrimagnet, and that Co2Ru0.5Mn0.5O4 undergoes an unusual magnetic double transition. Triple-axis measurements indicate that the lower temperature transition in Co2Ru0.5Mn0.5O4 is characterized by the onset of diffuse scattering and the emergence of short-range order. The Co2Ru1-xMnxO4 series appears to be well-suited for studying the coexistence of long- and short-range magnetic order.