Imaging of quantized magnetostatic modes using spatially resolved ferromagnetic resonance

We present a measurement technique for performing spatially resolved ferromagnetic resonance and directly imaging quantized magnetostatic modes in magnetic samples that undergo high frequency magnetic drive fields (up to 8 GHz). The dynamic response of a $\text{50×50\hspace{0.5em}μ}{\mathrm{m}}^2$ permalloy structure (100 nm thick) under a 7.04 GHz highly nonuniform drive field was measured as a function of the dc bias field using this technique. The magnetization variation observed indicates that quantized magnetostatic mode waves appear at certain bias fields, with the number of nodes decreasing with an increase in the bias field. We tentatively assign the indices of each mode using the Damon–Eshbach (DE) model. Similar modes have been observed for a similar sample geometry using an inductive measurement and they showed good agreement with the DE model. However, the result measured using this technique showed some discrepancy with the DE model and the spatial patterns observed are more complicated than simple one-dimensional standing waves. This complexity suggests that analysis beyond that of the DE model is required to explain the observations.