Exchange coupled magneto-optic layers

Abstract

Exchange coupled layers may provide solutions to a number of problems encountered in making magneto-optic storage media. In this work we show that it is possible to separate the storage function from the readout function by exchange coupling two layers, one with high MO rotation (readout layer) and the other with the coercivity and other properties necessary for small stable bits (storage layer). We have investigated the extent of coupling between a storage layer of Nd 10 Tb20 (FeCo)70 with Hc= 5.4 kG and θK= 17 min and several readout layer compositions with Hc≤1kG and θKof about 30 min. We find that the exchange coupling is weak unless both films have perpendicular easy axis anisotropy. The effect of varying the thickness of the readout layer (hRO) was studied keeping the storage layer thickness fixed. Coupled films with a coercivity of 1.7 kG and a θKof 33 min have been made. The rotation is about twice that of the storage layer alone and the coercivity is over three times that of the readout layer alone. © 1988 IEEE