Observation of Magnetoelastic Coupling by Spin-Wave Resonance

The method of spin‐wave resonance has been used to study the magnetoelastic coupling of spin waves and elastic waves over the frequency range from 57 GHz to 62 GHz in several nickel‐iron films of thicknesses of the order of 5000 Å. The film compositions have varied from 81Ni‐19Fe (zero magnetostriction) to 65Ni‐35Fe. For the latter composition, values have been obtained for the velocity of transverse sound‐waves in the film ${\mathrm{(v}}_t{\text{\hspace{0.17em}≈\hspace{0.17em}3×10}}^5\hspace{0.17em}\mathrm{cm}/\sec )$ , for the magnetoelastic coupling coefficient ${\text{(b\hspace{0.17em}≈\hspace{0.17em}−\hspace{0.17em}6×10}}^7\hspace{0.17em}\mathrm{erg}/{\mathrm{cm}}^3)$ , and for the phonon relaxation time ${\text{(τ\hspace{0.17em}≈\hspace{0.17em}2×10}}^{\text{−10}}\hspace{0.17em}\sec )$ at 77°K. A calculation combining the equations of motion for the magnetization and the strain‐wave equations under the appropriate boundary conditions for thin films, has provided fair theoretical agreement with the experimental data. However, there still remain points of disagreement concerning the width of the magnetoelastic interaction as a function of the wave‐vector. The strength of the observed interaction has been found to be directly proportional to $b$ , while its width in $\mathrm{k‐}\mathrm{space}$ has been found to be strongly dependent on ${\tau }^{\text{−1}}$ .