Time-Resolved Magnetization Dynamics and Damping Constant of Sputtered Co/Ni Multilayers

• Published in: IEEE transactions on magnetics 2011-10, Vol.47 (10), p.3036-3039
• Main Authors: Kato, T., Matsumoto, Y., Okamoto, S., Kikuchi, N., Kitakami, O., Nishizawa, N., Tsunashima, S., Iwata, S.
• Format: Article
• Language: English
• Subjects: Anisotropic magnetoresistance; Co/Ni multilayer; Cross-disciplinary physics: materials science; rheology; Damping; Exact sciences and technology; Gilbert damping; Magnetic multilayers; Magnetization; magnetization dynamics; Magnetomechanical effects; Materials science; Nickel; Nonhomogeneous media; Other topics in materials science; Physics; time-resolved magneto-optical Kerr effect (TRMOKE)
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2011.2158082

Co/Ni multilayers with a stack of Ta (2 nm)/[Co ( t Co )/Ni ( t Ni )] N /Ta (30 nm) were prepared by dc magnetron sputtering, and their magnetization dynamics were measured by time-resolved magneto-optical Kerr effect (TRMOKE). The total thickness of the multilayer and perpendicular anisotropy were varied by changing the bilayer period d = t Co + t Ni and number of repeats N while t Ni / t Co was kept at a constant of 2.5. The TRMOKE measurements show clear damped oscillation of the magnetization of Co/Ni multilayers after the pump pulse illumination, and the damping constant α of the Co/Ni multilayers was estimated from the TRMOKE waveform. The estimated α was found to be independent both on total thickness and anisotropy field of the multilayer and was estimated to be ~ 0.035 for all the multilayers. This means that the use of Ta capping and buffer layers is effective to evaluate intrinsic damping constant of the Co/Ni multilayer, and that independent control of α and perpendicular anisotropy are possible for the magnetic multilayers.