Nonresonant microwave absorption in epitaxial La_0.7Sr_0.3MnO₃ films and its relation to colossal magnetoresistance

Abstract

We study magnetic-field-dependent nonresonant microwave absorption and dispersion in thin La_0.7Sr_0.3MnO₃ films and show that it originates from colossal magnetoresistance. We develop a model for the magnetoresistance of a thin ferromagnetic film in an oblique magnetic field. The model accounts fairly well for our experimental findings, as well as for the results of other researchers. We demonstrate that nonresonant microwave absorption is a powerful technique that allows contactless measurement of magnetic properties of thin films, including magnetoresistance, anisotropy field, and coercive field.