Giant magnetoresistance with low saturation fields in Co-Fe/Cu and Ni₈₀Fe₂₀/Cu multilayers induced by optimized Ar acceleration voltage in ion beam sputtering

Magnetic properties and magnetoresistance were investigated for Co_1-xFe_x/Cu and Ni₈₀Fe₂₀/Cu multilayers with different Co_1-xFe_x, Ni₈₀Fe₂₀ and Cu thicknesses which were prepared on a MgO(110) substrate using ion beam sputtering with different Ar ion acceleration voltages (V_B). The MR ratio for highly Co composed Co-Fe/Cu multilayers was substantiated to be significantly larger than that for Co/Cu multilayers. The GMR strongly depended on V_B, suggesting the importance of interface randomness, which was investigated by ⁵⁹Co NMR measurements for Co/Cu multilayers. The uniaxial anisotropy was induced in the multilayers by epitaxial growth on a MgO(110) substrate. The uniaxial anisotropy leads to a low saturation field and quite a small field change needed for GMR which is indispensable for magnetic sensors such as MR heads.