Perpendicular magnetization and exchange bias in epitaxial NiO/[Ni/Pt]₂ multilayers

Abstract

The realization of perpendicular magnetization and perpendicular exchange bias (PEB) in magnetic multilayers is important for the spintronic applications. NiO(t)/[Ni(4 nm)/Pt(1 nm)]2 multilayers with varying the NiO layer thickness t have been epitaxially deposited on SrTiO3 (001) substrates. Perpendicular magnetization can be achieved when t < 25 nm. Perpendicular magnetization originates from strong perpendicular magnetic anisotropy (PMA), mainly resulting from interfacial strain induced by the lattice mismatch between the Ni and Pt layers. The PMA energy constant decreases monotonically with increasing t, due to the weakening of Ni (001) orientation and a little degradation of the Ni–Pt interface. Furthermore, significant PEB can be observed though NiO layer has spin compensated (001) crystalline plane. The PEB field increases monotonically with increasing t, which is considered to result from the thickness dependent anisotropy of the NiO layer.

Thickness-dependent magnetic properties in Pt/[Co/Ni] n multilayers with perpendicular magnetic anisotropy

“…The magnetic multilayers, e.g., [Co/Pd], [Co/Pt], and [Co/Ni], provide an opportunity to tune their magnetic properties by changing the thickness ratio controllably and the number of bilayer repeats thanks to the interface-induced PMA due to interfacial spin-orbit coupling and interfacial strain relevant magnetoelastic effects. [12][13][14][15][16][17] Among these PMA multilay-ers, the PMA [Co/Ni] multilayer also exhibits low damping constant, [14] which gets much attention, especially for the fields of current-driven auto-oscillation of magnetization and excitation and manipulation of spin-waves. [18,19] Furthermore, the PMA [Co/Ni] multilayer is also useful for spin-orbit torque devices.…”