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The thermal stability of sputtered TbFeCo thin films in magneto-optic quadrilayer structures containing Si3N4, SiO, and SiO2 dielectrics has been examined. The observed changes in coercivity upon annealing are attributed to two parallel mechanisms: structural relaxation in the amorphous magnetic alloy and preferential oxidation of Tb at the TbFeCo/SiO and TbFeCo/SiO2 interfaces. Kinetic modeling has revealed that a spectrum of activation energies is required to explain the relaxation data, whereas a single activation energy of 1.65 eV describes the oxidation process.

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Articles you may be interested inOptical properties of a multibeam column with a single-electron source An electron optical system with an array of columns was developed for an electron-beam addressable data storage device that has the form factor of Compact Flash and a capacity Ͼ10 GB. The electron optical column occupies an area Ͻ2500 m 2 and produces a focused beam with current Ͻ100 nA and a diameter Ͻ40 nm. An extended-area electron source that consists of an array of randomly distributed hemispherical-grain polysilicon nodules was developed. The field at the nodules is enhanced by a factor of 3-5 compared with metal-insulator-semiconductor structures with smooth cathodes. Electron emission consequently occurs predominantly at the nodules. A maximum current density of ϳ20 A/cm 2 was achieved with this electron source. The multiplicity of emission sites helps us to reduce significantly the emission current noise. An electron optical column to focus the emission from this extended source into a diameter Ͻ30 nm was also developed. The column consists of a single main lens and an array of auxiliary nanolenses. The main lens has a diameter of ϳ3 m. The distance between the main lens and the electron source is ϳ3 m. Each electron emission nodule has a self-aligned extraction electrode and a nanolens whose diameters are ϳ0.03-0.1 m. The nanolenses collimate the electron emission from the nodules. The main lens then focuses the collimated beams into a diameter of ϳ30 nm at an image distance of ϳ3 m. Without the nanolenses, the main lens alone can only focus the beam into a diameter of ϳ300 nm.