Magnetoelastic Waves in Yttrium Iron Garnet

Abstract

Magnetoelastic rf pulses with magnetically controlled echo time have been observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with power input in the milliwatt range. Excitation and detection was accomplished by placing a wire antenna near an optically flat end‐face of the rod. A nonuniform internal magnetic field was obtained by applying a steady, uniform external field parallel to the rod axis. The frequency‐time‐magnetic field characteristics have been measured. The behavior of these pulses can be explained in terms of a magnetoelastic disturbance traveling along the rod axis. It originates at that position along the axis where ω_c=γH_i. From there the disturbance travels to the nearer polished surface where it is reflected. On arrival back at the launch site a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence.