Sputtering Growth of Low-Damping Yttrium-Iron-Garnet Thin Films

Abstract

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 O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> MHz/T (or 2.82 MHz/Oe), which almost matches the standard value, and a Gilbert damping constant of α≈5.2 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> , 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.