Diffusion of Au and its influence on the coercivity of [FePt/Au/FePt]2x thin films during annealing in different atmospheres
2018
Abstract Influence of heat treatment atmosphere on magnetic properties of post-annealed [FePt(15 nm)/Au(7.5 nm)/FePt(15 nm)] 2x thin films was investigated. Thin films were deposited by dc magnetron sputtering at room temperature onto SiO 2 (100 nm)/Si(100) substrates and post-annealed in a temperature range of 500 °C–800 °C for 30 s in flowing Ar and Ar + H 2 (3 vol%) atmospheres. It was shown that hydrogen addition into annealing atmosphere allows to achieve high value of coercivity ~1671.1 kA/m after annealing at 600 °C. Such coercivity could be reached by heat treatment in pure Ar just after annealing at 700 °C. This effect could be related to acceleration of Au grain boundary diffusion into L1 0 -FePt phase. Such acceleration could be possible due to two reasons: hydrogen incorporation into Au crystal lattice, leading to interatomic bounds break and point defects formation; and hydrogen segregation at most defective areas, leading to cohesive energy decrease and upraise of significant stresses. As a result, nonmagnetic grid in grain boundaries of ferromagnetic material was formed at temperature lower by 100 °C.
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