Coexistence of singlet and ordered S=12 moments in the ground state of the triclinic quantum magnet CuMoO4

CuMoO4 is a triclinic quantum magnet based on S=1/2 moments at the Cu2+ site. It has recently attracted interest due to the remarkable changes in its chromic and volumetric properties at high temperatures and in its magnetic properties at low temperatures. This material exhibits a first-order structural phase transition at TC ∼ 190 K as well as a magnetic phase transition at TN ∼ 1.75 K. We report low-temperature heat capacity measurements as …