Exchange coupling of bilayers and synthetic antiferromagnets pinned to MnPt

Exchange bias and blocking temperature were studied in MnPt based bottom-pinned bilayers and synthetic antiferromagnets (SAF) prepared by magnetron sputtering. The structure and magnetic properties were determined as a function of the MnPt layer thickness. Exchange coupling was found to be (J(ex) = 0.4 erg/cm(2)) for a MnPt ( t <= 20 nm)/ CoFe (5 nm) bilayer. The distribution of the blocking temperature T-B was analyzed and its width Delta T-B and center point T-B,T-center determined. T-B is about 280 degrees C for thinner MnPt films, and increases to 330 degrees C for thick films. Delta T-B is constant for thick MnPt but steadily increases as the thickness decreases. SAF structures show higher exchange bias and higher T-B,T-center at thin layer thickness (t(MnPt) = 8.5 nm) compared to bilayers.