Coexistence of singlet and orderedS=12moments in the ground state of the triclinic quantum magnet CuMoO4 Academic Article uri icon

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abstract

  • 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 T_C ~ 190 K as well as a magnetic phase transition at T_N ~ 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 T_N. We observe neutron diffraction consistent with a simple (1/2, 0, 0) antiferromagnetic structure indicating a doubling of the a-axis periodicity below T_N. 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 non-magnetic singlets, and ferromagnetically-coupled spins coexisting within an antiferromagnetic structure below T_N ~ 1.75 K.

authors

  • Haravifard, S
  • Fritsch, K
  • Asano, T
  • Clancy, JP
  • Yamani, Z
  • Ehlers, G
  • Nishimura, T
  • Inagaki, Y
  • Kawae, T
  • Swainson, I
  • Gaulin, Bruce D

publication date

  • September 22, 2011