SPIN CONFIGURATION OF 2-DIMENSIONAL ORTHORHOMBIC LATTICE

We have applied the so-called macroscopic and microscopic methods of B ertaut to the two-dimensional problem of four spins in an orthorhombic lattice in order to investigate the spin configurations and spin-Hami ltonians for a two-dimensional orthorhombic lattice. We have determine d the propagation vectors of the modes and possible spin-Hamiltonians and concluded that the four collinear modes are along the z-axis and t he non-collinear modes are in the xy-plane of the two-dimensional orth orhombic lattice within the approximation of the model as long as seco nd order coupling of the modes is present.