Magnetic and Acoustic Excieations in Confined Nickel Nanowires

The magnetic and vibrational excitations of periodic arrays of Ni nanowires, in 1µmthick Al2 O3 membranes on Al substrates, have been investigated by Brillouin scattering. Ni nanowires of 30 and 40 nm diameter and periodicity of 100 nm have been studied in a transverse magnetic field from 0-0.4 T. The p-s polarized spectra feature three peaks, with Brillouin frequencies below 20 GHz, and whose intensities are strongly dependent on the applied magnetic field and whose Stokes/anti-Stokes intensity ratios are unequal. These results indicate that the three peaks are magnetic in origin. A surface acoustic wave on the Ni-filled Al2 O3 structures is also observed in p-p polarized spectra, with a phase velocity of about 3400 m/s for the 30nm-diameter nanowire sample.