

%% Spin wave spectrum
% We calculate the spin wave spectrum and compare it to published results.
% Since the momentum transfer vector *Q* has opposite sign in SpinW and in
% the published PRL paper, we change the sign manually here. Also for
% direct comparison, we calculate the spin-spin correlation function in the
% coordinate system commonly used for polarised neutron scattering 
% (x||Q, z perpendicular to the scattering plane). To define the scattering
% plane, we give two reciprocal space vectors in