Influence of variation of tungsten layer thickness on interfacial Dzyaloshinskii–Moriya interaction in W/CoFeB/SiO2 heterostructures

Interfacial Dzyaloshinskii–Moriya interaction (IDMI) is crucial for stabilizing skyrmions and chiral domain walls, which are expected to play key roles in the development of advanced spintronics-based devices. Using Brillouin light scattering spectroscopy, we have directly measured the W-layer thickness-dependent IDMI in technologically important W(t)/CoFeB/SiO2 heterostructures in the range 1 nm ≤ t ≤ 7 nm. Due to the presence of IDMI, a pronounced asymmetry is observed in the peak intensity, frequency and linewidth of the spin-wave spectra in the Damon-Eshbach geometry. Our study reveals that IDMI energy density increases monotonically for 1 nm ≤ t ≤ 5 nm, beyond which it decreases sharply, while its sign always remains negative. This remarkable variation of IDMI energy density is explained in the light of the thickness-dependent structural phase transition of W.