Propagating spin waves in nanometer-thick yttrium iron garnet films: Dependence on wave vector, magnetic field strength, and angle

Abstract

We present a comprehensive investigation of propagating spin waves in nanometer-thick yttrium iron garnet (YIG) films. We use broadband spin-wave spectroscopy with integrated coplanar waveguides (CPWs) and antennas on top of continuous and patterned YIG films to characterize spin waves with wave vectors up to 10 rad/μm. All films are grown by pulsed laser deposition. From spin-wave transmission spectra, parameters such as the Gilbert damping constant, spin-wave dispersion relation, group velocity, relaxation time, and decay length are derived, and their dependence on magnetic bias field strength and angle is systematically gauged. For a 40-nm-thick YIG film, we obtain a damping constant of 3.5×10-4 and a maximum decay length of 1.2 mm. We show a strong variation of spin-wave parameters with wave vector, magnetic field strength, and field angle. The properties of spin waves with small wave vectors change considerably with in-plane magnetic bias field up to 30 mT and magnetic field angle beyond 20?. We also compare broadband spin-wave spectroscopy measurements on 35-nm-thick YIG films with integrated CPWs and antennas and demonstrate that both methods provide similar spin-wave parameters.