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.