Ferromagnetic resonance depth profiles of magnetic tapes using frequency-dependent photoacoustic detection

Depth profiles of layered ferromagnetic tapes were studied using photoacoustically detected ferromagnetic resonance. The photoacoustic (PA) response was measured as a function of external magnetic field at different modulation frequencies ranging from 35 Hz to 23.5 kHz. The resonance pattern of the ferromagnetic coverlayer could be resolved in the recordings of the PA amplitudes at high frequencies. An estimate of the layer thickness was obtained from the observed PA phase angle shifts.