Techniques are disclosed for carrying out ferromagnetic resonance (FMR) testing on whole wafers populated with one or more buried magnetic layers. The techniques can be used to verify or troubleshoot processes for forming the buried magnetic layers, without requiring the wafer to be broken. The techniques can also be used to distinguish one magnetic layer from others in the same stack, based on a unique frequency response of that layer. One example methodology includes moving a wafer proximate to a waveguide (within 500 microns, but without shorting), energizing a DC magnetic field near the target measurement point, applying an RF input signal through the waveguide, collecting resonance spectra of the frequency response of the waveguide, and decomposing the resonance spectra into magnetic properties of the target layer. One or both of the DC magnetic field and RF input signal can be swept to generate a robust set of resonance spectra.