Magnetic properties and the interfacial Dzyaloshinskii-Moriya interaction in exchange biased Pt/Co/NixOy films

Abstract We show that a trilayer magnetic structure, consisting of a heavy metal (Platinum) as a buffer, an ultrathin ferromagnet (Cobalt) as a functional layer, and an antiferromagnetic insulator (Nickel oxide, NixOy) as a capping, is a host of intriguing physical phenomena desirable for spintronics. X-ray photoelectron spectroscopy revealed changes in the ratio of NixOy phases with different stoichiometry. Due to strong spin-orbit coupling, the Pt layer induces perpendicular magnetic anisotropy in Co, breaks its structural inversion symmetry, and causes an additive effect of Pt/Co and Co/NixOy interfaces to the effective interfacial Dzyaloshinskii-Moriya interaction (Deff). Manipulation the magnetic anisotropy can be realized by the ferromagnetic layer thickness variation and modification of the Co/NixOy interface. The NixOy capping layer induces the exchange bias in Co, which effective field |Beb| can be controlled in the range from 0 to 24 mT. The magnitude and direction of Beb does not affect Deff. The increase of Ar pressure leads to structural transformation of the Co/NixOy interface and, consequently, to decrease of the surface Dzyaloshinskii-Moriya interaction (Ds), the source of which is the NiO phase. We demonstrate that the studied Pt/Co/NixOy system has a number of functional properties useful for future logic and memory applications.