Influence of the top and bottom interface on perpendicular magnetic anisotropy in Tb-Fe-Ag multilayers

Mossbauer spectroscopy (CEMS), vibrating-sample magnetometry and the polar magneto-optic Kerr effect (MOKE) have been employed to investigate the effect of either "top" (Tb-deposited-on-Fe) or "bottom" (Fe-deposited-on-Tb) interfaces, or of both types of interfaces, on magnetic properties of UHV-grown Tb-bcc-Fe-Ag multilayers. All samples develop perpendicular Fe-spin texture, perpendicular magnetic anisotropy, polar remanence, and large polar coercivities upon cooling; however, the T-dependence is found to be different for different types of interfaces. The remanent-magnetized state of the Fe-layers at low T is either nearly a perpendicular single-domain state or a nearly perpendicular multidomain state, both states being characterized by canted Fe-spins or canted easy axes (cone state). The shape of MOKE hysteresis loops is found to be wavelength dependent. Qualitatively, all effects may be correlated with differences in Tb-Fe interface roughness.