Magnetic properties of amorphous nanocolumns created by heavy ion irradiation of paramagnetic YCo2 thin films (invited)

Publisher Website
Google Scholar
Abstract
Recent studies have demonstrated the possibility of inducing amorphous latent tracks in metallic materials by GeV heavy ion irradiation. In the present work, 0.880 GeV 238U beams have been used to induce ferromagnetic amorphous nanocolumns in nonmagnetic crystalline YCo2 films. The loss of crystallinity deduced by x‐ray analysis is in good agreement with the one determined by magnetic measurements. The Co magnetic moment in the columns is approximately equal to 1 μB, as in bulk amorphous YCo2, but the ordering temperature (150 K) is strongly reduced with respect to the bulk. Magnetization measurements reveal the nanocolumns to be single domain. A perpendicular anisotropy is observed in samples irradiated at the smallest fluencies, which is interpreted to be due to shape anisotropy. A progressive decrease of the anisotropy with increasing fluence is observed and qualitatively described in terms of dipolar interactions between columns. At low temperature, the coercive field reaches 650 Oe. A simple nonuniform magnetization reversal process is suggested.