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 H_k increases sharply with the addition of Tb while the coercivity H_ch along the hard axis and H_ce 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 4πM_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 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.