Exchange-coupled FePt/Fe bilayers with perpendicular magnetisation

A bilayer made up of a hard (FePt) and soft (Fe) phase coupled by exchange interactions is fabricated with the easy-magnetisation direction perpendicular to the film plane. Structural characterization is performed by means of X-ray diffraction, X-ray reflectivity and transmission electron microscopy. The films morphology is investigated by atomic force microscopy and their magnetic properties are studied at room temperature by an alternating gradient force magnetometer. A high surface roughness and the compositionally homogeneous FePt layer is found. Consistent with the observed microstructure, the hysteresis loops measured on the FePt film show a strong orientation with high uniaxial anisotropy, and perpendicular coercivity while that of the FePt/Fe bilayer exhibits an increase in saturation magnetisation, remanence, and energy product.