Fe spin structure in Tb/Fe multilayers

摘要

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 respectively) with perpendicular magnetic anisotropy (PMA) and large coercivity at low temperatures was investigated by Fe-57 Mossbauer spectroscopy, the polar magneto-optical Kerr effect, and superconducting quantum interference device magnetometry. A spontaneous reversible temperature-driven Fe spin reorientation transition from orientation parallel to the film plane to an out-of plane orientation (with Fe spins tilted by an angle [theta] relative to the film normal direction) was observed upon cooling below the reorientation 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 increase 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 structure, composition and Fe spin orientation within Fe-on-Tb and Tb-on-Fe interfaces are reported. [References: 40]