The interfacial Dzyaloshinskii-Moriya interaction (IDMI) is investigated in ${\mathrm{Co}}_2\mathrm{FeAl}$ (CFA) ultrathin films of various thicknesses ($0.8\mathrm{nm}\le t_{\mathrm{CFA}}\le 2\mathrm{nm}$) grown by sputtering on Si substrates, using Pt, W, Ir, and MgO buffer or/and capping layers. Vibrating sample magnetometry reveals that the magnetization at saturation ($M_s$) for the Pt- and Ir-buffered films is higher than the usual $M_s$ of CFA due to the proximity-induced magnetization (PIM) in Ir and Pt estimated to be 19% and 27%, respectively. The presence of PIM in these materials is confirmed using x-ray resonant magnetic reflectivity. Moreover, while no PIM is induced in W, higher PIM is obtained with Pt when it is used as a buffer layer rather than a capping layer. Brillouin light scattering in the Damon-Eshbach geometry is used to investigate the thickness dependences of the IDMI constants from the spin-wave nonreciprocity and the perpendicular anisotropy field versus the annealing temperature. The IDMI sign is found to be negative for $\mathrm{Pt}/\mathrm{CFA}$ and $\mathrm{Ir}/\mathrm{CFA}$, while it is positive for $\mathrm{W}/\mathrm{CFA}$. The thickness dependence of the effective IDMI constant for stacks involving Pt and W shows the existence of two regimes similar to that of the perpendicular anisotropy constant due to the degradation of the interfaces as the CFA thickness approaches a critical thickness. The surface IDMI and anisotropy constants of each stack are determined for the thickest samples where a linear thickness dependence of the effective IDMI constant and the effective magnetization are observed. The interface anisotropy and IDMI constants investigated for the $\mathrm{Pt}/\mathrm{CFA}/\mathrm{MgO}$ system show different trends with the annealing temperature. The decrease of the IDMI constant with increasing annealing temperature is probably due to the electronic structure changes at the interfaces, while the increase of the interface anisotropy constant is coherent with the interface quality and disorder enhancement.

• Received 30 October 2017
• Revised 22 January 2018

DOI:https://doi.org/10.1103/PhysRevApplied.9.044044