creates different predefined spin models obj = SW_MODEL(model, param, {fid}) Input: model String, name of the model, one of the following: 'triAF' Triangular lattice Heisenberg antiferromagnet in the ab plane (a=b=3 Angstrom), with gamma = 120 deg angle and optimised magnetic structure. Arbitrary number of Heisenberg interaction can be defined, param(1) gives the value of 1st neighbor interaction, param(2) the second etc. 'squareAF' Square lattice antiferromagnet. 'chain' Chain with further neighbor interactions. param Input parameters of the model, depending on which is selected. fid Where to print the text output. Default is 1 to print to the Command Window. Optional. Output: obj sw class object with the selected model. See also SW.