Interlayer coupling in spin valves studied by broadband ferromagnetic resonance

Abstract

The magnetization dynamics of coupled and uncoupled spin valves with the structure $\mathrm{NiFe}\phantom{\rule{0.28em}{0ex}}(20\phantom{\rule{0.28em}{0ex}}\mathrm{nm})/\mathrm{Cu}({t}_{\mathrm{Cu}})/\mathrm{NiFe}\phantom{\rule{0.28em}{0ex}}(20\phantom{\rule{0.28em}{0ex}}\mathrm{nm})/\mathrm{IrMn}\phantom{\rule{0.28em}{0ex}}(10\phantom{\rule{0.28em}{0ex}}\mathrm{nm})$ is probed by broadband ferromagnetic resonance absorption measurements. The coupling intensity between the free and the pinned layers is tailored by varying the Cu thickness ${t}_{\mathrm{Cu}}$. Broadband spectra exhibited two resonant modes for each value of the applied field. It is observed that the coupling between NiFe layers modifies the amplitude of the absorption peaks and the shape of the dispersion relations for each mode, which becomes particularly distorted in the antiparallel magnetization state. The observed phenomena are well described by applying a semianalytical model that properly takes into account the coupling interactions and allows an efficient numerical calculation of the absorption peak amplitudes and the dispersion-relation shapes.