Preparation of Soft Magnetic Films of Nanocrystalline Fe-Cu-Nb-Si-B Alloy for Low Noise Backlayers

Soft magnetic thin films of nanocrystalline Fe-Cu-Nb-Si-B alloy were deposited using the facing targets sputtering(FTS) apparatus. It was found that the Fe-Cu-Nb-Si-B single layers thinner than 100 nm exhibited large saturation magnetization 4πMs of 11.3 kG and high relative permeability μr of 500. In addition, μr of the films deposited under the application of the external field of 100 Oe increased up to about 1400. However, when these films were thicker than 100 nm, their soft magnetic properties degraded due to the appearance of perpendicular magnetic anisotropy. On the other hand, μr of the post-annealed films thinner than 120 nm increased drastically up to around 6200 owing to the release of internal stress of the films.