XPS and AES studies on the interface between metal and polymer layers: The effect of Ar-plasma treatment of the polymer surface preceding the metal deposition

Several kinds of direct overwrite schemes have been proposed for magneto‐optic media. Schemes using weakly coupled multilayers have shown great promise. In these methods, control of exchange coupling is key to realizing overwrite. An intermediate layer between the memory and reference layers is used sometimes to control the degree of exchange coupling and interface wall energy density. For this purpose, GdFeCo layer having in‐plane anisotropy has been used previously. However, it is easily oxidized. Also, these multilayer direct overwrite media are comprised of similar materials but with different concentrations of components. The components from one layer may diffuse into the adjacent layer, rendering direct overwrite impossible. We found that easily polarizable metals such as Pd can be used as an interlayer to control the degree of exchange interaction between memory and reference layers. Pd metal has no magnetic moment by itself, but a moment is induced on it when it is in proximity to a magnetic material. This induced magnetic moment can mediate the exchange interaction between the reference and memory layers. Since Pd is noble, a very thin layer of Pd (10–20 A) is stable and prevents diffusion between the magnetic layers.

Control of exchange coupling for direct overwrite media using Pd metal interlayer

This study provides a method for improving the corrosion resistance of rare‐earth–transition‐metal films used for magneto‐optical recording without depressing the recording sensitivity. This was attained by increasing Co content and substituting Dy for Tb and TbFeCo amorphous films. Potentiostatic polarization measurements indicate that the pitting potential of the film increases with the increase of Co content up to y=0.17 for (Tb0.5Dy0.5)0.21Fe0.79−yCoy. Attempts are made to explain the results using Auger electron spectroscopy and x‐ray photoelectron spectroscopy. For the above‐noted composition, both the Kerr rotation angle and coercivity observed through the substrate retain their initial values after the accelerated aging test. Results indicate that the (Tb0.5Dy0.5)0.21Fe0.62Co0.17 film offers superior characteristics for corrosion resistance without disturbing the magnetic properties.

Corrosion‐resistant‐rare‐earth–transition‐metal amorphous films with high recording sensitivity for magneto‐optical disks

The study of rare-earth metal oxidation by AES

Depth-profile of amorphous TbFeCo film sputtered onto polycarbonate substrate was studied by X-ray photoelectron spectroscopy. Oxidized metals, oxides and hydroxides for example, and adsorbed impurities were found to exist mainly in the vicinity of the film surface and film/substrate interface. Multiplet splitting of core-level spectra was also observed to estimate the degree of charge transfer from rare earth to transition metal. The splitting was identical with that of pure metal which indicates extremely small charge transfer.

T. Satoh

Papers

X-ray photoelectron spectroscopy studies on amorphous TbFeCo alloy and polycarbonate interface