Saturation fields in Co-Fe/Cu multilayers with giant magnetoresistance: In-plane uniaxial magnetic anisotropy effects

Magnetization processes are investigated by calculation and experiments for Co-Fe/Cu multilayers with giant magnetoresistance, which are prepared on MgO(110) substrates using ion beam sputtering and have in-plane uniaxial magnetic anisotropy (K_u). The experiments show the metamagnetic transition from antiferromagnetic spin structure to ferromagnetic one for an easy axis external field. This is supported by calculation of the magnetic phase diagram for stable magnetization configurations, which shows the metamagnetic transition to occur for (J₁₂/d)/K_u≤1, where J ₁₂ is antiferromagnetic layer interaction and d is magnetic layer thickness. The saturation fields from antiferromagnetic to ferromagnetic spin structures are substantially decreased by induction of the in-plane uniaxial anisotropy. The relation H_sh - 2H_se = 2K _u/M_s, found for the saturation fields by the calculation, is confirmed experimentally for the multilayers, where M_s is the saturation magnetization, and H_se and H_sh are the saturation fields for the external field parallel to the easy and hard axes, respectively.