High Magnetic Anisotropy Field in CoZr Thin Films

Magnetic properties and high frequency characteristics of Co_100-xZr_x (x=5-17) thin films have been investigated. The experimental results show that with the increase of Zr content, the saturation magnetization, 4πM_s, decreases from 12.3 kG for x=5 to 7.3 kG for x=17; induced anisotropic field, H_k, of the films increases from 232 Oe for x=5 at first and reaches a maximum value of 266 Oe for x=9; coercivive force along hard and easy direction, H_ch and H_ce, ranges 1.6-7.1 Oe and 5.4-10.9 Oe, respectively. The highest ferromagnetic resonance frequency, f_FMR of 4.9 GHz could be achieved for the films with x=9. In addition, H_ch and H_ce are reduced by adopting Cu underlayer or Ni₂₀Fe₈₀ underlayer to the studied CoZr films. The optimal magnetic properties of 4πM_s=12 kG , H_ce=5.4 Oe, H_ch=0.7 Oe, H_k=258 Oe , ρ = 233 μΩ-cm and f_FMR=5 GHz are obtained for Co₉₁Zr₉(110 nm)/Ni₂₀Fe₈₀(15 nm) bilayer.