Crystallization and high temperature functional properties in CoFeB films

• Interplay between crystallization and temperature dependent magnetization is demonstrated in thermomagnetic curves.
• Pronounced changes in electrical resistivity and optical reflectance with temperature are observed.
• The activation barrier for crystallization is electrically determined to be 1.32 eV.

CoFeB alloy films have been attracting much research interest for the applications in magnetoelectronic devices. In this study, crystallization and high temperature functional properties in the sputtered CoFeB alloy films were investigated. The as-deposited alloy films were amorphous and a nanocrystalline structure was formed after annealing, confirmed by X-ray measurements. Large variation in saturation magnetization with temperature was observed in thermomagnetic measurements, reflecting the interplay between crystallization and temperature dependent magnetization in the ferromagnetic alloy film. Pronounced changes in electrical resistivity and optical reflectance with temperature were observed in the alloy film, in accompany with the structural change. The activation barrier for crystallization was determined to be 1.32 eV from the electrical measurements, showing a good thermal stability of the alloy film.