Sputtering Growth of Low-Damping Yttrium Iron Garnet Thin Films

This letter reports the development of low-damping yttrium-iron-garnet (YIG) thin films via sputtering. The films were deposited by sputtering at room temperature first and were then annealed in O2 at high temperature. It is found that the annealing temperature critically affects the structural properties of the YIG films and thereby dictates the static and dynamic properties of the films. A 75 nm thick YIG film annealed at 900 °C shows an rms surface roughness of 0.08 nm, a coercivity of only 14 A/m (or 0.18 Oe), a saturation induction of 0.1778 T (or 1778 G), which is very close to the bulk value, a gyromagnetic ratio of 2.82 × 104 MHz/T (or 2.82 MHz/Oe), which almost matches the standard value, and a Gilbert damping constant of α a 5.2 × 10–5, which is the lowest among the values reported so far for magnetic films in the nanometer thickness range. Frequency-dependent ferromagnetic resonance measurements with different field orientations confirmed that two-magnon scattering, if present, is very weak, and the measured damping value represents the actual damping of the YIG film.