Spin waves modes in the AFM and helicoidal phases of CuO

Cupric oxide (CuO) has a helical magnetic phase in the temperature range from 213 to 230K which exhibits impoper ferroelectricity (i.e. the magnetic order couples to the crystal structure which creates a voltage across the sample). We aim to determine the microscopic interactions responsible for stabilizing the helical structure and generating ferroelectricity. The key to unlocking these subtle interactions can be found in the magnon dispersion. In previous unpolarized and polarized neutron inelastic scattering studies there was found to be up to 8 magnon modes (dynamical oscillations of the Cu spins) at low energies. Our objective is to use the excellent energy and momentum resolution of LET to resolve these modes, enabling us to develop a complete model for the Cu spin dynamics which explains the improper ferroelectric behaviour. .