  We report the structural, magnetic, and interfacial spin transport properties
of epitaxial terbium iron garnet (TbIG) ultrathin films deposited by magnetron
sputtering. High crystallinity was achieved by growing the films on gadolinium
gallium garnet (GGG) substrates either at high temperature, or at room
temperature followed by thermal annealing, above 750 {\deg}C in both cases. The
films display large perpendicular magnetic anisotropy (PMA) induced by
compressive strain, and tunable structural and magnetic properties through
growth conditions or the substrate lattice parameter choice. The ferrimagnetic
compensation temperature (TM) of selected TbIG films was measured through
temperature-dependent anomalous Hall effect (AHE) in Pt/TbIG heterostructures.
In the studied films, TM was found to be between 190-225 K, i.e., approximately
25-60 K lower than the bulk value, which is attributed to the combined action
of Tb deficiency and oxygen vacancies in the garnet lattice evidenced by x-ray
photoelectron spectroscopy measurements. Sputtered TbIG ultrathin films with
large PMA and highly tunable properties reported here can provide a suitable
material platform for a wide range of spintronic experiments and device
applications.
