Recent development in cobalt-base metallic glasses

Abstract

Metallic glasses are produced by rapid quenching methods or quasi-statically at slow cooling by the effective control of potent heterogeneous nucleation sites. Metallic glasses are mostly prepared by melt spinning technique. Curie temperature, hardness, soft ferrimagnetisms, saturation magnetization, coercive force, permeability and respective transitional properties for glass state to crystal state have been studied. The crystal transition properties are affected by temperature, enthalpy and activation energy. Time-temperature-transformation (TTT) diagrams for amorphous to crystal transition have been obtained using Johnson-Mehl-Avrami equation. Based on compositions, additions in small amounts and metalloid contents transformation is classical as polymorphic or ordering or split types etc. Below crystallization temperature the Von-Mises criteria determine the yield processes in amorphous state. Effects of annealing and stress induced annealing have been studied on crystallization, magnetic properties, order-disordered phase transitions, structural relaxation, quasi-first order transformations and thermoelastic damping. Existence of crystallites in amorphous matrix or proportional content of crystallites in a system affects magnetism in multilayered thin films. Measurements of magneto-resistance, magnetic after effect, extent of magnetization, magnetic stability and magnetic anisotropy and zeromagnetostrictive properties have been done. Interrelations among magnetic properties, temperature, crystal texture, crystal orientation and microstructure for magnetic recording media that require high coercivity in relation to crystal anisotropy perpendicular to the film substrate have been examined. Electrochemical deposition and modifications of existing sputtering techniques have been introduced for preparation of thin films.