  Here we demonstrate nanometer thick iron garnet films suitable for the
magneto-optical applica-tions. Bismuth-substituted iron garnet films of
compositions Bi{_1}Y{_2}Fe{_5}O{_{12}} and Bi{_1}Tm{_2}Fe{_5}O{_{12}} deposited
on gadolinium gallium garnet substrate are fabricated and characterized. Their
thicknesses range from 2 to 10 nm, which corresponds to just a few crystal
lattice constants. Faraday rotation of the nanofilms reaches 29.7 deg/{\mu}m at
420 nm which is comparable and even a bit better than single crystal micrometer
thick films of similar composition. The film surface morphology by atomic force
microscopy gives root mean square (RMS) roughness of the nanofilms as small as
0.13 nm that is also similar to the RMS of single crystal micrometer thick
films. The Bi{_1}Tm{_2}Fe{_5}O{_{12}} films demonstrate effective uniaxial
anisotropy. These all make the fabricated nanofilms very promising for their
po-tential applications in magneto-optical devices and quantum technologies.
