Soft magnetic multilayer films with wide frequency band losses and high resistivity

A series of CoFeB/MgO multilayers was fabricated by means of DC/RF magnetron sputtering. It is observed that the electromagnetic properties of the multilayers of CoFeB/MgO are closely related with the thickness of CoFeB sublayers, and the soft magnetic properties of discontinuous multilayers are affected by the cycle number of CoFeB/MgO bilayers. The optimized film of [Co 64 Fe 24 B 12 (0.7 nm)/MgO(0.4 nm)] 50 exhibits a magnetic loss µ ″ larger than 100 and µ ′ larger than 80 between 0.9 and 2.1 GHz. The electrical resistivity ρ of this film is as high as 3.75 × 10 3  µΩ cm. The results indicate that this discontinuous CoFeB/MgO multilayer film has potential to serve as a noise suppressor or EMC materials in the GHz frequency range.