Analysis of medium-double layer garnet film interaction in a parallel high density magnetooptic read head

Multitrack readout using the magnetooptic Faraday effect in garnet films has improved the density of information. The garnet films are Bi-substituted YIG samples that can resolve down to about 2 μm² . A double garnet layer has been used to improve the interaction between the garnet and the magnetic tape. The first layer has its magnetization parallel to the plane of the film, while the outer layer´s is perpendicular. The contribution of the first layer allows better guiding of the field lines of the magnetic tape. This can be understood in terms of the mirror effect, whereby the system consisting of the tape and the double layer is equivalent to a single layer (perpendicular) twice as thick that is coupled twice to the magnetic tape. It is found that the best configuration for the in-plane film is a flux-closure-domain configuration, because its anisotropy constant is much lower than that of the perpendicular layer