Fe spin structure in Tb/Fe multilayers

The Fe spin structure in ultrahigh-vacuum-deposited hcp Tb(t(Tb))/bcc Fe(t( Fe)) multilayers (t(Tb) and t(Fe) are the Tb and Fe layer thicknesses respe ctively) with perpendicular magnetic anisotropy (PMA) and large coercivity at low temperatures was investigated by Fe-57 Mossbauer spectroscopy, the p olar magneto-optical Kerr effect, and superconducting quantum interference device magnetometry. A spontaneous reversible temperature-driven Fe spin re orientation transition from orientation parallel to the film plane to an ou t-of plane orientation (with Fe spins tilted by an angle [theta] relative t o the film normal direction) was observed upon cooling below the reorientat ion temperature T-R. At a fixed value of t(Tb), T-R was found to follow a t (Fe)(-1) behaviour, indicating that the PMA originates from the interfaces. Upon cooling, the perpendicular remanent magnetization shows a step-like i ncrease near the magnetic ordering temperature of Tb, contrary to [theta](T ), which exhibits no such anomaly. Apparently, strong coupling of Fe layers via magnetic Tb layers affects the perpendicular magnetic domain structure at remanence. Further, Fe-57 probe layer Mossbauer results concerning stru cture, composition and Fe spin orientation within Fe-on-Tb and Tb-on-Fe int erfaces are reported.