Blocking temperature in exchange coupled MnPt∕CoFe bilayers and synthetic antiferromagnets

Exchange coupled Mn51.5Pt48.5∕Co90Fe10 bottom-pinned bilayers and synthetic antiferromagnets (SAFs) were prepared by magnetron sputtering. Exchange bias, coercivity, and blocking temperature were determined as a function of the MnPt thickness. Interfacial exchange energy was found to be Jex=0.4erg∕cm2 for a Mn51.5Pt48.5(t⩾20nm)∕Co90Fe10 (5nm) bilayer. Thermal stability of the bilayers was analyzed by separation of the blocking temperature distribution in (a) width ΔTB and (b) center temperature TB,center of the distribution. For thick MnPt films ΔTB is constant but steadily increases for thin films. SAF structures show higher exchange coupling and higher blocking temperatures at thin layer thickness (tMnPt=8.5nm).