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

CoNbZr films for an adjustable magnetic anisotropy field Hk 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 Hch along the hard axis and Hce 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 4πMs of 8.9 kG, a hard axis coercivity Hch of 1.79 Oe, a easy axis coercivity Hce of 1.4 Oe and a magnetic anisotropy field Hk of 87 Oe. The measured ferromagnetic resonance frequency fFMR of this film is 2.30 GHz. The real permeability μ′ is about 100, which is maintained up to 2 GHz. In addition, there is a broad band of the imaginary permeability μ″ 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.