Domain-wall motion and interfacial Dzyaloshinskii-Moriya interactions inPt/Co/Ir(tIr)/Tamultilayers

Abstract

The interfacial Dzyaloshinskii-Moriya interaction (DMI) is important for chiral domain walls (DWs) and for stabilizing magnetic skyrmions. We study the effects of introducing increasing thicknesses of Ir, from zero to 2 nm, into a Pt/Co/Ta multilayer between the Co and Ta. We observe a marked increase in magnetic moment, due to the suppression of the dead layer at the interface with Ta, but the perpendicular anisotropy is hardly affected. All samples show a universal scaling of the field-driven domain wall velocity across the creep and depinning regimes. Asymmetric bubble expansion shows that DWs in all of the samples have the left-handed Néel form. The value of in-plane field at which the creep velocity shows a minimum drops markedly on the introduction of Ir, as does the frequency shift of the Stokes and anti-Stokes peaks in Brillouin light scattering measurements. Despite this qualitative similarity, there are quantitative differences in the DMI strength given by the two measurements, with BLS often returning higher values. Many features in bubble expansion velocity curves do not fit simple models commonly used to date, namely a lack of symmetry about the velocity minimum and no difference in velocities at high in-plane field. These features are explained by the use of a model in which the depinning field is allowed to vary with in-plane field in a way determined from micromagnetic simulations. This theory shows that velocity minimum underestimates the DMI field, consistent with BLS returning higher values. Our results suggest that the DMI at an Ir/Co interface has the same sign as the DMI at a Pt/Co interface.

Strength and length scale of the interaction between domain walls and pinning disorder in thin ferromagnetic films

“…where [18] for details on the fitting procedure). This finding is compatible with the results reported for a large variety of other magnetic materials [13,14,18,21,22] and confirms that chiral and nonchiral DWs follow very similar universal behaviors as predicted in Ref. [11] for the creep regime.…”

“…1. For their analysis, we used the self-consistent description of the creep and depinning regimes [13,14,18,21,22]:…”

Spin Waves in Thin Films and Magnonic Crystals with Dzyaloshinskii–Moriya Interactions

“…Moreover, there is no need to neglect or approximate the dipolar interactions, as in the case of DW-based methods. As can be seen from Tables 5.2 and 5.3, some groups have measured the DMI strength with both BLS and DW-based methods, where different values of D are found [81,127]. The theoretical model developed previously has been applied to analyze experimental observations of the strength of the DM constant in Pt(d HM )/CoFeB films.…”

Nonvolatile Ionic Modification of the Dzyaloshinskii-Moriya Interaction

“…The origin of the discrepancies between these two sets of values remains an open question. Discrepancies between D values obtained by DW motion experiments under in-plane fields and BLS have already been reported and attributed to the difference in length scales probed by each technique [21] or by the limitations of a simplified model in more complex scenarios [27]. In this context, an inhomogeneous D in the film could be responsible for the discrepancy.…”

“…The simulated disorder introduced here is based on the typical grain size values found in the literature for this type of material. The individual variation of the experimental parameters for each grain is introduced randomly in the 0-20% range which constitutes an average of 10%, also a typical value [27,32]. The simulations presented in Fig.…”