Magnetoresistance enhancement in a perpendicular (Co/Pt)4/Co/IrMn/(Co/Pt)2/Co structure.

We investigate the magnetoresistance (MR) effect and magnetic properties in (Co/Pt)₄/Co/IrMn (SFM) and (Co/Pt)₄/Co/IrMn/(Co/Pt)₂/Co (DFM) structures with (Co/Pt)₄/Co and (Co/Pt)₂/Co multilayers having a perpendicular magnetic anisotropy. Despite the exchange bias field, the antiferromagnetic IrMn layer itself influences the coercivity (H_c) and MR differently for both types of structures when the IrMn layer is thin. A suppressed H_c and an enhanced MR in the DFM samples are obtained compared with those in the SFM samples. The maximum MR reaches up to (0.6 ± 0.1)% when the IrMn thickness (t_IrMn) of the DFM samples varies from 1.5 to ∼5 nm, but the MR value of the SFM samples remains (0.1 ± 0.05)% with the same t_IrMn range. The suppressed H_c and the enhanced MR in the DFM samples may be due to the formation of an antiferromagnetic-type contact when large antiferromagnetic domains in the IrMn layer are sandwiched by (Co/Pt)₄/Co and (Co/Pt)₂/Co multilayers. [ABSTRACT FROM AUTHOR]