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

S. Haravifard, K. Fritsch, T. Asano, J. P. Clancy, Z. Yamani, G. Ehlers, T. Nishimura, Y. Inagaki, T. Kawae, I. Swainson, B. D. Gaulin

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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 well as extensive elastic and inelastic neutron scattering measurements on powder samples taken above and below TN. We observe neutron diffraction consistent with a simple (1/2, 0, 0) antiferromagnetic structure indicating a doubling of the a-axis periodicity below TN. In addition, inelastic neutron scattering above a spin gap of ∼2.3 meV is consistent with triplet excitations out of paired S=1/2 moments which form singlet dimers. Low-lying spin wave excitations are also observed and these originate from ordered S=1/2 moments below T N. Taken together these measurements show the ground state of CuMoO4 to display both nonmagnetic singlets and ferromagnetically coupled spins coexisting within an antiferromagnetic structure below T N ∼ 1.75 K.

Original languageEnglish
Article number094436
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number9
Publication statusPublished - Sept 22 2011

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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