Microscopic model for the tensorial surface anisotropy field observed in thin yitrium-iron garnet film spin-wave resonance

A microscopic model for the surface parameter in thin YIG films is proposed to explain the observed properties of the non-propagating surface spin-wave. This theory proposes two surface interactions. The first is a temperature dependent molecular field coupling between the surface iron atoms and the gadolinium atoms at the film substrate interface. The second interaction is a single ion anisotropy due to Fe²⁺ ions present at the surface resulting from the migration of oxygen vacancies during annealing. Excellent agreement is observed between the experimental results and the prediction of the microscopic theory.