title: Spin Hall Magnetoresistance in Metallic Bilayers.
abstract: Spin Hall magnetoresistance (SMR) is studied in metallic bilayers that consist of a heavy metal (HM) layer and a ferromagnetic metal (FM) layer. We find a nearly tenfold increase of SMR in W/CoFeB compared to previously studied HM/ferromagnetic insulator systems. The SMR increases with decreasing temperature despite the negligible change in the W layer resistivity. A model is developed to account for the absorption of the longitudinal spin current to the FM layer, one of the key characteristics of a metallic ferromagnet. We find that the model not only quantitatively describes the HM layer thickness dependence of SMR, allowing accurate estimation of the spin Hall angle and the spin diffusion length of the HM layer, but also can account for the temperature dependence of SMR by assuming a temperature dependent spin polarization of the FM layer. These results illustrate the unique role a metallic ferromagnetic layer plays in defining spin transmission across the HM/FM interface.
authors.affiliation: National Institute for Materials Science, Tsukuba 305-0047, Japan.
authors.forename: Junyeon
authors.initials: J
authors.lastname: Kim
authors.affiliation: National Institute for Materials Science, Tsukuba 305-0047, Japan.
authors.forename: Peng
authors.initials: P
authors.lastname: Sheng
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Saburo
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: National Institute for Materials Science, Tsukuba 305-0047, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Mitani
authors.affiliation: National Institute for Materials Science, Tsukuba 305-0047, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Hayashi