Investigation of Magnetic Anisotropy and Damping in Obliquely Sputtered Cobalt Thin Films

A systematic investigation of the magnetic anisotropy (MA) in cobalt thin films as a function of thickness (10-60 nm) is performed employing angular-dependent longitudinal magneto-optic Kerr effect (L-MOKE) and ferromagnetic resonance (FMR) spectroscopy techniques. All the Co films were polycrystalline with very low interface roughness (< 0.5 nm) as gauzed by X-ray diffraction and X-ray reflectivity measurements. The magnetic coercivity in all the samples was found to be very sensitive to the crystallite size and surface roughness. Both MOKE and FMR measurements conclusively suggest the presence of dominant in-plane uniaxial magnetic anisotropy in all the samples. A quantitative analysis of the anisotropy is also performed, considering the possibility of the presence of the cubic anisotropy. The study reveals the unique role of deposition geometry on the MA, which is fundamentally interesting and beneficial for designing next-generation information storage devices, spin-transfer torque magnetic random-access memories, and spin torque nano-oscillators.