Anomalous temperature variation of interlayer exchange coupling in CoFe/Bi/Co trilayers

In this study different temperature dependences have been observed for ferromagnetic (FM) and anti-ferromagnetic (AFM) couplings. A theoretical modeling will be proposed in the presentation to account for this unusual thermal effect. CoFe/Bi/Co sandwich samples were synthesized using dc sputtering at room temperature. The crystal structure and the cross-sectional microstructures of the films were investigated by X-ray diffraction (XRD) using Cu-Kalpha radiation and 300 KeV high-resolution transmission electron microscopy (HRTEM). The magnetic properties were determined from a vibrating sample magnetometer (VSM).The representative magnetization loops of trilayer samples with various spacer thicknesses measured at 150K, 200K and 300 K respectively were determined.