Nonlinear Effects of Z-Directed Spin Waves in Thin Films

A calculation is made for the high‐power instability of the Z‐directed spin waves in a thin insulating ferromagnetic film. For complete pinning, the critical field is found to be $${\mathrm{(\gamma h)}}^2{\mathrm{=\Delta }}_n^3{n}^2{\pi }^2\text{[9}\sqrt{3}{\mathrm{(\omega }}_M+\frac{1}{3}{\omega }_{\mathrm{ex}}{a}^2{k}_n^2{\mathrm{)]}}^{\text{−1}}$$ . The calculation is also made for the critical field, assuming a mixed boundary condition.