Electric-field control of perpendicular magnetic anisotropy in multiferroic PZT- and PMN- PT//[Co/Ni] composites with negative magnetostriction
Daniel B. Gopman, Andrew P. Chen, Cindi L. Dennis, June W. Lau, Robert D. Shull, Gregory P. Carman, Peter Finkel, Margo Staruch, Andres Chavez
A longstanding goal of spintronics is to identify alternatives to current-generated Oersted- fields for magnetization control at the nanoscale. An emerging approach seeks to harness the voltage-induced strain in a proximal piezostrictive layer to modify the magnetic anisotropy orientation of a ferromagnetic layer by the inverse magnetostriction effect. This article presents the electric-field control of perpendicular magnetic anisotropy in multilayered films of Cobalt and Nickel grown on top of piezoelectric substrates. A broadband ferromagnetic resonance spectroscopy technique with in-situ electric-field biasing reveals changes to the perpendicular magnetic anisotropy in response to strains transferred from the piezoelectric substrate. The changes in magnetic anisotropy correspond to saturation magnetostriction strengths that range from -20x10-6 to -50x10-6 for Ni-rich and Co-rich multilayers, respectively. This moderate negative magnetostriction enables the design of a Co(0.2)/Ni(0.4) multilayered film that exhibits an electrically-mediated 90 degree magnetization reorientation that can be cycled reversibly between a perpendicular magnetic anisotropy and an in-plane magnetic anisotropy. Reversible, electric-field mediated magnetization reorientation in Co/Ni multilayers can pave the way for applications of electric-field control of magnetism in non- volatile technologies.