Substrate heating effects on ferromagnetic CoFeB thin films

Damping in ferromagnetic alloys such, as Co₄₀Fe₄₀B₂₀ are very sensitive to thermal effects both during deposition and post deposition. Depositions using and alloyed Co₄₀Fe₄₀B₂₀ target were done on si (100) and amorphous glass substrates at room temperature up to 500°C. The samples deposited onto si (100) at 500°C crystalized into face centered cubic (110) Co₇Fe₃ whereas the samples on glass remained amorphous. The gilbert damping parameter α was reduced from .0141 to .0095 when deposited on glass however increased from .0097 to .0131 on si (100) at temperatures from 20°C- 400°C. At low deposition temperatures on glass large metallic grains of 50-75nm were found. The crystallization of Co₄₀Fe₄₀B₂₀ to Co₇Fe₃ at 500°C resulted in broader ferromagnetic resonance peak-to-peak line widths of 1050 Oe and increased in plane coercivity values of 200 Oe compared to 35 Oe and 5 Oe for amorphous Co40Fe40B20. Post deposition annealing of Co₄₀Fe₄₀B₂₀ on si (100) from 20-350°C showed reductions in damping from .0131 to .0076 and effective magnetization increased from 11.8 kOe to 13.3 kOe.