  In this study, we address the impact of Ti underlayer thickness (UL: 0-40 nm)
on the structural, magnetic, and microscopic properties of TbFe thin films. The
structural analysis confirmed the intermixing at interfaces of the Ti and TbFe
layer with the increment of UL thicknesses. Out-of-plane (OOP) coercivity (Hc),
and saturation field (Hs) gradually increased with an increase in UL thickness
regardless of interface mixing. For UL = 10 nm, the domain contrast and OOP
stray field strength were enhanced, which may be due to the extent of d-d
hybridization dominated over the influence of interfacial roughness. While for
UL = 20, and 40 nm, the extent of interfacial roughness dominated the
hybridization effects and as a result, stray fields deteriorated. By placing UL
of 20 nm, Hc increased by nearly 6 times more than the bare TbFe system. So, we
observe a state with high OOP Hc combined with nearly zero OOP stray fields
that are found to co-exist in the sample. The magnetization reversal studies on
a large area reveal domain nucleation followed by domain-wall motion in all the
films. The idea of tuning magnetic properties by varying thicknesses of Ti UL
may useful in spintronics applications.
