We prepared by vapor deposition at room temperature thin (500 Å) Co/Pt multilayers or layered structures directly onto glass or Si substrates. They show a preferential magnetization perpendicular to the film plane for Co thicknesses below 12 Å and a 100% perpendicular remanence for Co thicknesses below 4.5 Å. The magnetic anisotropy can be explained by an interface contribution to the anisotropy. We also investigated the magneto-optical (MO) polar Kerr effect of these multilayers. Because of their excellent magnetic properties and their potentially high oxidation and corrosion resistance, these Co/Pt-layered structures are very promising candidates for MO recording. The Kerr rotation θk at λ=820 nm for a 35×(4.0 Å Co+12.7 Å Pt)-layered structure, which has 100% magnetic remanence, is modest (−0.12°), but the reflectivity R is high (70%), which results in a respectable figure of merit Rθ2k. Furthermore, the Kerr effect increases towards shorter wavelengths and thus favors future higher-density recording.

Oscillations with a period of two Cr monolayers were measured in the antiferromagnetic exchange coupling between Fe magnetizations separated by Cr. The coupling was measured on a sample consisting of a Au(20 A)/Fe(50 A)/Cr(0-18 A wedge) film deposited by a molecular-beam epitaxy on a Fe[lOO] single-crystal "whisker." The Cr and Fe grew monolayer by monolayer as monitored by reflection high-energy-electron diff'raction. The coupling was determined from the magneto-optic Kerr effect. It was antiferromagnetic for 5-18 A Cr with four strong peaks and a maximum value of -0.60 mJ/m^ for eight monolayers of Cr.

The factors that influence the coercive field Hc and the shape of the magnetic hysteresis loop for Co/Pt multilayers (MLs), applied as a magneto-optical (MO) recording medium, have been investigated. The hysteresis loop of MLs, made by evaporation of Kr sputtering, became more rectangular when the total film thickness was reduced, i.e., the saturation field Hs decreased and the nucleation field Hn increased. Hs was calculated using a stripe domain model and Hn was modeled assuming that nucleation took place at a field that destabilized small vestigial magnetic domains. Both models assumed that domain walls can move in the ML film and the agreement with experiment was good. However, these models could not explain the hysteresis loops for the MLs deposited on a thick Pt base layer or made at high sputter gas pressure. These MLs showed a more particulate microstructure and the hysteresis loop was sheared, consistent with magnetic reversal by uniform rotation rather than domain-wall motion. From thermomagnetic recording experiments it was concluded that these latter MLs were less suitable as a MO recording medium because of higher noise in spite of the larger Hc. Co/Pt disks made by either evaporation or Kr sputtering showed lower noise and a higher carrier-to-noise ratio than those deposited on a Pt base layer or made by Ar sputtering.