Surface-acoustic-wave-driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers

Surface acoustic waves (SAW) were generated on a thin layer of the ferromagnetic semiconductor (Ga,Mn)(As,P). The out-of-plane uniaxial magnetic anisotropy of this dilute magnetic semiconductor is very sensitive to the strain of the layer, making it an ideal test material for the dynamic control of magnetization via magnetostriction. The amplitude and phase of the transmitted SAW during magnetic field sweeps showed a clear resonant behavior at a field close to the one calculated to give a precession frequency equal to the SAW frequency. A resonance was observed from 5 to 85 K, just below the Curie temperature of the layer. A full analytical treatment of the coupled magnetization/acoustic dynamics showed that the magnetostrictive coupling modifies the elastic constants of the material and accordingly the wave-vector solution to the elastic wave equation. The shape and position of the resonance were well reproduced by the calculations, in particular the fact that velocity (phase) variations resonated at lower fields than the acoustic attenuation variations. We suggest one reinterpret SAW-driven ferromagnetic resonance as a form of resonant, dynamic, delta-E effect, a concept usually reserved for static magnetoelastic phenomena.