Effects of geometrical asymmetry on spin modes in a Fe/Cr/Fe/Cr/Fe/Cr (211) trilayer -- Presentazione poster by R. Zivieri - Conferenza nazionale

We report a study of a Fe(20 Å)/Cr/Fe(20 Å)/Cr/Fe(100 Å) trilayer with ferromagnetic coupling between the first and the second Fe films and antiferromagnetic (AF) coupling between the second and the third Fe films. Our aim is to highlight the effects of the geometrical asymmetry on spin modes frequencies vs applied field H and on the Brillouin light scattering (BLS) intensity peaks. A first effect is the presence of a minimum in the low-frequency branch at H = 0.4 kOe due to a first-order phase transition absent in the correspondent symmetric case. The consequence on the BLS measured and calculated spectra is the interchange of the highest peak from the Stokes to the anti-Stokes side. In addition, there is an increase of the frequency gap between the low and the intermediate branch during the second-order phase transition primarily caused by the different anisotropy fields generated by the ferromagnetic films. We also explain the maximum in the low-branch dispersion for H around 2.5 kOe in terms of a prevalence of biquadratic exchange coupling in this region. -- Presentazione poster by R. Zivieri - Conferenza nazionale