Yttrium iron garnet (YIG) is a ferrimagnetic material which is widely used in various microwave and optical-communication devices and other applications - mainly due to its suitable magnetic and magneto-optical properties. In addition, YIG is used as a host material for solid-state lasers together with better-known YAG, YLF and YVO₄.

Properties of YIG:

• Faraday rotation: -3000-(-4000) degrees/cm (Ce-doped YIG films)
• Saturation magnetization: 1800-2500 G (bulk YIG at room temperature)
• Curie temperature: 550 K

YIG is also transparent to wavelengths exceeding 600 nm, which makes it a good candidate for atom-optical purposes, in particular, for realizing new kinds of atom traps. Transparency is needed since our idea to construct the trap is based on combining the the repulsive potential caused by an evanescent electromagnetic field with the attractive potential formed by a static magnetic field. In this case, the magnetic field is produced by permanent-magnet structures patterned in the surface of a YIG film.

We have deposited thin YIG films on Gadolinium Gallium Garnet (GGG) substrates (film thickness of the order of 50-100 nm). GGG is an appropriate substrate material for YIG since the lattice constant and thermal expansion coefficients match with those of YIG. GGG is also a paramagnetic substance, and thus the substrate doesn't perturb the magnetic field that would be induced by the YIG structure. The films show relatively smooth surfaces - the droplet density is < 10⁶ um^-2, which is sufficiently low for small structures to be patterned into the film. The in-plane magnetization of the films was measured with a SQUID magnetometer at the Wihuri Physical Laboratory of the University of Turku. The best samples exhibit magnetization that is at least 50 % of the bulk value. This is a value high enough for our applications.