Interfacial Dzyaloshinskii-Moriya interaction in the epitaxial W/Co/Pt multilayers.

The Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered ferromagnetic films gives rise to non-colinear spin structures stabilizing magnetization configurations with nontrivial topology. In this work magnetization reversal, magnetic domain alignment, and strength of DMI are related to the crystalline structure of W/Co/Pt multilayers grown by molecular beam epitaxy. The applied growth method enables the fabrication of layered systems with higher crystalline quality than commonly applied sputtering techniques. A relatively high value of the D coefficient was determined from the aligned magnetic domain stripe structure, substantially exceeding 2 mJ m-2. The highest value of DMI strength Deff = 2.64 mJ m-2 and surface DMI parameter DS = 1.83 pJ m-1 have been observed for a repetition number equal to 10. The experimental results correlate exactly with those obtained from the micromagnetic modelling and density functional theory calculations performed for the well-defined layered stacks. This high value of DMI strength originates from the additive contributions of the interfacial atomic Co layers at the two types of interfaces.

XMCD studies of magnetic polarization at Mo atoms in CoMo alloy and magnetically coupled Co/Mo multilayers.

Magnetic polarization of Mo atoms in Co96Mo4 alloy film and Co/Mo multilayered structures has been studied by X-ray magnetic circular dichroism. Samples with Mo spacers of two different thicknesses (0.9 nm and 1.8 nm) were investigated. Mo atoms receive a magnetic moment of -0.21µB in the alloy. In the multilayer with the thinner Mo spacer (dMo = 0.9 nm) the magnetic moment is much smaller (-0.03µB). In both cases the measured induced moment at the Mo site is oriented antiparallel to the moment at the Co atoms. The presence of the induced moment in the Mo spacer coincides with antiferromagnetic coupling between the Co component slabs. In contrast, neither measurable induced moment at the Mo site nor interlayer coupling between the Co layers has been found for the multilayer with the thicker Mo spacer. Possible mechanisms of the coupling associated with the induced moment are discussed in detail.