SMITH et al, 2001. A quantitative determination of magnetic fluctuations in CuGeO3. European Physical Journal B, 21(3), pp. 341-347
A polarised neutron scattering investigation has been carried out on a powder sample of CuGeO3
within the temperature range of 1.5 K to 600 K. The magnetic scattering has been separated from all other
contributions by using polarised neutrons and polarisation analysis and placed onto an absolute scale. At
low temperatures the long wavelength components of the paramagnetic response are suppressed consistent
with the formation of Cu dimers in which the magnetic moments are correlated antiferromagnetically.
This form of the scattering persists to temperatures well above the dimerisation temperature Tsp 14 K.
However as the temperature is raised the intensity of the long wavelength spin fluctuations increases
and above 150 K they are the dominant feature in the wave vector dependence of the response. At all
temperatures the observed scattering extrapolates smoothly to the Q = 0 value given by the uniform
susceptibility. Consequently the thermal variation of the uniform susceptibility arises from the evolution of
the long wavelength magnetic fluctuations. At large wave vectors the energy dependence of the scattering
revealed that the response occurs below 16 meV in agreement with the reported maximum magnetic
excitation energy at the zone boundary in the ground state. However the total magnetic scattering is
signi cantly less than that expected for a local moment system suggesting that the spectrum of thermal
and quantum fluctuations overlap.