title: Novel room-temperature spin-valve-like magnetoresistance in magnetically coupled nano-column Fe3O4/Ni heterostructure.
abstract: Herein, we design a room-temperature spin-valve-like magnetoresistance in a nano-column Fe3O4/Ni heterostructure without using a non-magnetic spacer or pinning layer. An Fe3O4 nano-column film is self-assembled on a Ni underlayer by the thermal decomposition method. The wet-chemical self-assembly is facile, economical and scalable. The magnetoresistance (MR) response of the Ni underlayer in the heterostructure under positive and negative out-of-plane magnetic fields differ by ∼0.25 at room temperature and ∼0.43 at 100 K. We attribute the spin-valve-like magnetoresistance to the unidirectional magnetic anisotropy of the Ni underlayer when being magnetically coupled by the Fe3O4 nano-column film. The out-of-plane negative-field magnetization is higher than the positive-field magnetization, affirming the unidirectional magnetic anisotropy of the Fe3O4/Ni heterostructure. Temperature-dependent magnetic and resistivity studies illustrate a close correlation between the magnetization transition of Fe3O4 and resistivity transition of Ni and prove a magnetic coupling between the Fe3O4 and Ni. First-principles calculations reveal that the Fe3O4/Ni model under a negative magnetic field is energetically more stable than that under a positive magnetic field. Furthermore, partial density of states (PDOS) analysis demonstrates the unidirectional magnetic anisotropy of the Ni 3d orbital. This is induced by the strong ferromagnetic coupling between Fe3O4 and Ni via oxygen-mediated Fe 3d-O 2p-Ni 3d hybridizations.
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg and Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-01 Innovis, Singapore 138634, Singapore.
authors.forename: Wen
authors.initials: W
authors.lastname: Xiao
authors.affiliation: Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-01 Innovis, Singapore 138634, Singapore.
authors.forename: Wendong
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg.
authors.forename: Tun Seng
authors.initials: TS
authors.lastname: Herng
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg and Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-01 Innovis, Singapore 138634, Singapore.
authors.forename: Qing
authors.initials: Q
authors.lastname: Qin
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg.
authors.forename: Ming
authors.initials: M
authors.lastname: Zheng
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg.
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Hong
authors.affiliation: Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
authors.forename: Yuan Ping
authors.initials: YP
authors.lastname: Feng
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore. msedingj@nus.edu.sg.
authors.forename: Jun
authors.initials: J
authors.lastname: Ding