Coupling dependent reversal in Co/Pt based mixed anisotropy multilayer stacks

Abstract A series of multilayers [Co(6)/Pt(15)]4/(Pt(s))/[Co(10)/Pt(15)]4 (thicknesses in A) consisting from a perpendicular magnetic anisotropy [Cο(6)/Pt(15)]4-stack (PA) coupled to an in-plane anisotropy [Cο(10)/Pt(15)]4-stack (IPA) through the variable Pt interlayer (with s = 0–45 A), is studied as a model mixed-anisotropy system. Vector vibrating sample magnetometry and polarized neutron reflectometry show that, at remanence, the magnetization of each stack relaxes to its own easy axis, with the exception of the s = 0. For the s = 0 sample, the strong coupling between the two different anisotropy stacks results in a collective reversal of both stacks. This process corresponds to an averaged effective uniaxial anisotropy, which suppresses the PA characteristics. For the rest of the samples the stacks are weakly coupled and separate reversal of the two stacks occurs. The PA stack reverses by rapid domain wall motion under the influence of the IPA which has relaxed to its own easy plane. The remaining coupling, despite being weak, influences the values and angular dependence of the reversal fields as well as the positions of positive/negative and doublets on the First Order Reversal Curve (FORC) distributions.