Preparation and FMR analysis of Co nanowires in alumina templates

Magnetic and structural properties of a high aspect ratio Co nanowire (NW) array electrodeposited in free-standing porous alumina template with a pore diameter of ∼200 nm are studied. Considered collectively, X-ray diffraction analysis, magnetometer and ferromagnetic resonance (FMR) measurements indicate that both the c-axis of crystal structure and the easy axis of magnetization are aligned preferentially perpendicular to the NW axis. The FMR spectra are characterized with very broad (a few kG) breadths and exhibit asymmetric shape in low field region due to under-saturation effects. Surprisingly, FMR spectra also revealed the presence of a spin-wave mode (SWM) as the applied field direction approached parallel to the film plane, i.e. perpendicular to the NWs. A brief discussion on this observation is provided. Further, characteristic magnetic parameters of the studied NW array were obtained by fitting the field angle-dependent FMR spectra and resonance field by using an analytical model that considers various factors affecting the total anisotropy.