  An enhancement of the spin-orbit effects arising on an interface between a
ferromagnet (FM) and a heavy metal (HM) is possible through the strong breaking
of the structural inversion symmetry in the layered films. Here we show that
the introduction of an ultrathin W interlayer between Co and Ru in Ru/Co/Ru
films enables to preserve perpendicular magnetic anisotropy (PMA) and
simultaneously induce a large interfacial Dzyaloshinskii-Moriya interaction
(iDMI). We find that the Ru/Co/W/Ru films have PMA up to 0.35 nm of the nominal
thickness of W (tW). The study of the spin-wave propagation in the
Damon-Eshbach geometry by Brillouin light scattering (BLS) spectroscopy reveals
the drastic increase of the iDMI value with the rising tW. The maximum iDMI of
-3.1 erg/cm2 is observed for tW=0.24 nm, which is 10 times larger than the
latter for the quasi-symmetrical Ru/Co/Ru films. The ability to simultaneous
control the strength of PMA and iDMI in symmetrical HM/FM/HM trilayer systems
through the interface engineered inversion asymmetry at the nanoscale excites
new fundamental and practical interest to the chiral ferromagnets, which are a
potential host for magnetic skyrmions.
