A NEW MAGNETO-OPTIC ENHANCEMENT EFFECT IN MACROSCOPIC FERRIMAGNETS

Optical and magneto-optic properties at room temperature of Co-1-x(EuS )(x) evaporated thin films are presented over a wide photon-energy ran ge. Co-1-x(EuS)(x) belongs to a new class of phase-separated magnetic materials, called macroscopic ferrimagnets, in which two magnetic phas es couple antiferromagnetically across the phase boundary. Polar Kerr rotations of up to 2 degrees are observed in Co rich samples (x less t han or equal to 0.3) at photon energies of 4.5 eV. The high Kerr rotat ion coincides with a distinct decrease in reflectivity suggesting an o ptical enhancement effect. A model calculation indicates a new type of enhancement based on the relative index of refraction at the phase bo undary between the Co matrix and the EuS precipitate particles,