Time-Dependent Landau-Ginzburg Modelling of Magnetic Inhomogeneities and Spiral Domain Structures in Thin Films

ABSTRACTA Landau-Ginzburg model for a uniaxial ferromagnetic thin film is presented which includes inhomogeneities due to nearest neighbor exchange interactions. The role of external magnetic fields is studied in the determination of exact symmetries of the equation of state. Spiral domain structures allowed by symmetry considerations as exact solutions at the critical and tricritical points have recently been found experimentally in epitaxially grown single-crystal garnet ferrite films. These experiments are discussed from the point of view of our model.