Thin Solid Films, Vol.658, 12-21, 2018
Diffusion of Au and its influence on the coercivity of [FePt/Au/FePt](2x) thin films during annealing in different atmospheres
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 SiO2(100 nm)/Si(100) substrates and post-annealed in a temperature range of 500 degrees C-800 degrees 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 similar to 1671.1 kA/m after annealing at 600 degrees C. Such coercivity could be reached by heat treatment in pure Ar just after annealing at 700 degrees 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 degrees C.