Temperature-dependent interlayer exchange coupling strength in synthetic antiferromagneticPt/Co₂/Ru/Co/Pt₄ multilayers

In this work, we experimentally investigated the thermal stability of the interlayer exchange coupling field (H_ex) and strength (-J_iec) in synthetic antiferromagnetic (SAF) structure ofPt(0.6)/Co(0.6)₂/Ru(t_Ru)/Co(0.6)/Pt(0.6)₄ multilayers with perpendicular anisotropy. Depending on the thickness of the spacing ruthenium (Ru) layer, the observed interlayer exchange coupling can be either ferromagnetic or antiferromagnetic. The H_ex were studied by measuring the magnetization hysteresis loops in the temperature range from 100 K to 700 K as well as the theoretical calculation of the -J_iec. It is found that the interlayer coupling in the multilayers is very sensitive to the thickness of Ru and temperature. The H_ex exhibits either a linear or a non-linear dependence on the temperature for different thickness of Ru. Furthermore, our SAF multilayers show a high thermal stability even up to 600 K (H_ex=3.19 kOe, -J_iec=1.97 erg/cm² for t_Ru=0.6 nm, the unit 1 Oe=79.5775 A·m^-1), which was higher than the previous studies.