Characterizing the diffuse continuum excitations in the classical spin liquid h-YMnO3

We extend previous inelastic neutron scattering results on the geometrically frustrated antiferromagnet hexagonal-YMnO3, 3 , which has been suggested to belong to the class of classical spin liquids. We expand the energy transfer range of the diffuse signal up to 6.9 meV within a wide temperature range around the ordering temperature, T N . The two distinct diffuse signals in the a-b b plane, the signal localized at P ' and the scattering intensity connecting P ' points over the M', ' , are shown to be only weakly energy dependent. In addition, an external magnetic field of up to 10.5 T applied along c is shown to have no effect on the diffuse signal. In the orthogonal scattering plane, the signals are shown to be dependent on l only through the magnetic form factor, showing that the correlations are purely two-dimensional, and supporting the origin of this to be the frustrated Mn3+ 3 + triangles. This result is corroborated by atomistic spin dynamics simulations showing similar scattering vector and temperature behaviors. Lastly, data for the spin wave scattering in the (h, h , 0, , l ) plane allow for a discussion of the magnetic ground state where better agreement is found between the data and an ordered structure of the P 1 or P 3 symmetry, albeit crystal electric field arguments dismiss the P 1 as a possibility.