title: Magnetic domain patterns on strong perpendicular magnetization of Co/Ni multilayers as spintronics materials: I. Dynamic observations.
abstract: Materials with perpendicular magnetic anisotropy can reduce the threshold current density of the current-induced domain wall motion. Co/Ni multilayers show strong perpendicular magnetic anisotropy and therefore it has become a highly potential candidate of current-induced domain wall motion memories. However, the details of the mechanism which stabilizes the strong perpendicular magnetization in Co/Ni multilayers have not yet been understood. In the present work, the evolution of the magnetic domain structure of multilayers consisting of pairs of 2 or 3 monolayers (ML) of Ni and 1 ML of Co on W(110) was investigated during growth with spin-polarized low-energy electron microscopy. An interesting phenomenon, that the magnetic domain structure changed drastically during growth, was revealed. In the early stages of the growth the magnetization alternated between in-plane upon Co deposition and out-of-plane upon Ni deposition. The change of the magnetization direction occurred within a range of less than 0.2 ML during Ni or Co deposition, with break-up of the existing domains followed by growth of new domains. The Ni and Co thickness at which the magnetization direction switched shifted gradually with the number of Co/Ni pairs. Above 3-4 Co/Ni pairs it stayed out-of-plane. The results indicate clearly that the Co-Ni interfaces play the important role of enhancing the perpendicular magnetic anisotropy.
authors.affiliation: Fundamental Electronics Research Institute, Osaka Electro-Communication University, Neyagawa, Osaka 572-8530, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Suzuki
authors.forename: Kazue
authors.initials: K
authors.lastname: Kudo
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kojima
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yasue
authors.forename: Noriko
authors.initials: N
authors.lastname: Akutsu
authors.forename: Wilson Agerico
authors.initials: WA
authors.lastname: Diño
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kasai
authors.forename: Ernst
authors.initials: E
authors.lastname: Bauer
authors.forename: Takanori
authors.initials: T
authors.lastname: Koshikawa
mesh_terms: D016880:Anisotropy; D003035:Cobalt / Q000737:chemistry*; D060526:Magnetic Fields; D008422:Materials Testing; D008567:Membranes, Artificial; D009532:Nickel / Q000737:chemistry*; D012542:Scattering, Radiation
chemical_list: D008567:Membranes, Artificial; D003035:Cobalt; D009532:Nickel