Ultrahigh frequency magnetic susceptibility of Co and Fe cylindrical films deposited by pulsed laser ablation.

Soft magnetic Co and Fe films were deposited by pulsed laser ablation on Cu wires. The circular magnetic susceptibility of the cylindrical films was measured by applying an ac circular magnetic field at frequencies up to 6 GHz. The measured ferromagnetic resonance frequency of the Co films was 2.5 GHz, and the real part of the magnetic susceptibility at the lowest frequency of our measurements was 150. These results were explained as solutions of the Landau-Lifshitz-Gilbert equation, taking into account that the easy magnetization direction of the Co films was along the wire axis. Further measurements with an axial external magnetic field were consistent with this view. In contrast, for the Fe films, significant values of the circular magnetic susceptibility were measured only in the presence of external magnetic fields applied along the wire axis. This result indicated that the easy magnetization direction of the Fe films was not along the Cu wire axis. The magnetic anisotropy of both Co and Fe cylindrical films might originate from magnetoelastic effects, resulted from built-in stress. The different behaviors of the Co and Fe cylindrical films would then be attributable to the different signs of their magnetostriction constants λs. [ABSTRACT FROM AUTHOR]