Tb doped CoNbZr soft magnetic films with high anisotropy field for applications in GHz frequency region

CoNbZr films for an adjustable magnetic anisotropy field H-k by doping with rare-earth of different atomic ratio Tb element were obtained in this work. The effect of Tb addition ranged from 0 to 4 at.% on the magnetic properties of the amorphous CoNbZr films was further investigated. The results show that the magnetic anisotropy field Hk increases sharply with the addition of Tb while the coercivity H,h along the hard axis and H,, along the easy axis change slightly with increasing Tb content in the films. As a consequence, CoNbZr film doped with 2 at.% of Tb exhibits excellent soft magnetic properties with a saturation magnetization 4 pi M-s of 8.9 kG, a hard axis coercivity H-ch of 1.79 Oe, a easy axis coercivity H-ce of 1.4 Oe and a magnetic anisotropy field H-k of 87 Oe. The measured ferromagnetic resonance frequency f(FMR) of this film is 2.30 GHz. The real permeability mu' is about 100, which is maintained up to 2GHz. In addition, there is a broad band of the imaginary permeability mu '' over a large frequency band, indicating high losses. Therefore, Tb doped CoNbZr film is an excellent candidate for high frequency applications such as electromagnetic interference suppressors. (C) 2007 Published by Elsevier B.V.