u2+ atoms with S = 1/2 spin on a
% square lattice. Exchange parameters are taken from the paper:
% R. Coldea, Phys. Rev. Lett. *86*, 5377 (2001).
% The exchanges are corrected for the ring exchange but the energy
% renormalization factor included in the paper is not applied.

J   = 138.3;
Jp  = 2;
Jpp = 2;
Jc  = 38;

lacuo = sw_model('squareAF',[J-Jc/2 Jp-Jc/4 Jpp]/2,0);
lacuo.unit_cell.S = 1/2;
plot(lacuo,'range',[2 2 1])

%% Magnon dispersion and intensity
% We plot the magnon dispersion and the neutron s