One of the main interests of polarized neutrons and full polarization analysis is to allow a clear separation of magnetic contributions from the nuclear (structural) ones.
An example of such a separation is shown here for the high-Tc supoerconducting cuprate YBa2Cu3O6.85. The incident polarization is kept parallel to the scattering vector, in such a manner that the magnetic fluctuations contribute only to the spin-flip (SF) channel and the structural excitations to the non-spin-flip (NSF) channel. These results demonstrate unambiguously the magnetic nature of the resonant peak at 41 meV and the existence of a spin gap around 25 meV.
In the opposite figure, the energy dependence of the background is due to the increased counting time at higher incident energies. The shaded area illustrates the magnetic signal peaking at the resonance position of 41 meV.