90° magneto-optical Kerr rotation: Criteria of existence and features

An analysis is made of the general properties required for a magnetic material to exhibit 90{degree} polar Kerr rotation. The approach is phenomenological invoking general properties of the dielectric tensor relating to the energy absorption. It is shown that the effect exists only if the absorptive part of the dielectric tensor is equal to zero. We identify ranges of Re {var_epsilon}{sub xx}({omega}) and Im {var_epsilon}{sub xx}({omega}) where 90{degree} rotation is realized, and study the Kerr ellipticity, the reflectivity, and the magneto-optical signal in these regions. {copyright} {ital 1997} {ital The American Physical Society}