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Register a new userNon-reciprocity of spin wave propagation induced by the interface Dzyaloshinskii-Moriya interaction in Py/Pt film structures
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Results of a comprehensive study by means of Brillouin spectroscopy, complemented by Ferromagnetic Resonance characterization, of spin waves (SW) propagating in Py/Pt bi-layers, characterized by pronounced interface Dzyaloshinskii-Moriya interactions (IDMI) are reported. Non-conventional wave behavior of SW travelling in opposite directions, characterized by non-reciprocity with respect to the inversion of the sign of the SW wave-number, has been revealed. The value of the effective IDMI constant D has been estimated.
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The Dzyaloshinskii-Moriya interaction (DMI) has been shown to stabilise Ne{e}l domain walls in magnetic thin films, allowing high domain wall velocities driven by spin current effects. DMI occurs at the interface between ferromagnetic and heavy metal layers with strong spin-orbit coupling, but details of the interaction remain to be understood and the role of proximity induced magnetism (PIM) in the heavy metal is unknown. We report interfacial DMI and PIM in Pt determined as a function of Au and Ir spacer layers in Pt/Co/Au,Ir/Pt. The length-scale for both interactions is sensitive to sub-nanometre changes in the spacer thickness, and they correlate over sub mono-layer spacer thicknesses, but not for thicker spacers. The spacer layer thickness dependence of the Pt PIM for both Au and Ir shows a rapid monotonic decay, while the DMI changes rapidly but has a two-step approach to saturation and continues to change, even after the PIM is lost.
Employing Brillouin spectroscopy, strong interfacial Dzyaloshinskii-Moriya interactions have been observed in an ultrathin Pt/CoFeB film. Our micromagnetic simulations show that spin-wave nonreciprocity due to asymmetric surface pinning is insignificant for the 0.8nmthick CoFeB film studied. The observed high asymmetry of the monotonic spin wave dispersion relation is thus ascribed to strong Dzyaloshinskii-Moriya interactions present at the Pt/CoFeB interface. Our findings should further enhance the significance of CoFeB as an important material for magnonic, spintronic and skyrmionic applications.
Interfacial Dzyaloshinskii-Moriya interaction (iDMI) in interlayer exchange coupled (IEC) Pt/Co$_{20}$Fe$_{60}$B$_{20}$(1.12 nm)/Ru/Co$_{20}$Fe$_{60}$B$_{20}$(1.12 nm) systems have been studied theoretically and experimentally. Vibrating sample magnetometer has been used to measure their magnetization at saturation and their interlayer exchange coupling constants. These latter are found to be of an antiferromagnetic nature for the investigated Ru range thickness (0.5-1 nm). Their dynamic magnetic properties were studied using Brillouin light scattering (BLS) technique. The BLS measurements reveal pronounced non-reciprocal spin waves propagation. In contrast to the calculations for symmetrical IEC CoFeB layers, this experimental nonreciprocity is Ru thickness and thus coupling strength dependent. Therefore, to explain the experimental behaviour, a theoretical model based on the perpendicular interface anisotropy difference between the bottom and top CoFeB layers has been developed. We show that the Ru thickness dependence of the spin wave non-reciprocity is well reproduced by considering a constant iDMI and different perpendicular interfacial anisotropy fields between the top and bottom CoFeB layers. This anisotropy difference has been confirmed by the investigation of the CoFeB thickness dependence of effective magnetization of Pt/CoFeB/Ru and Ru/CoFeB/MgO individual layers, where a linear behaviour has been observed.
Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI) which gives rise to topological spin textures, such as skyrmions. However, the DMI has not yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping for spin waves. In this work, we experimentally evidence the interfacial DMI in a 7~nm-thick YIG film by measuring the nonreciprocal spin wave propagation in terms of frequency, amplitude and most importantly group velocities using all electrical spin-wave spectroscopy. The velocities of propagating spin waves show chirality among three vectors, i.e. the film normal direction, applied field and spin-wave wavevector. By measuring the asymmetric group velocities, we extract a DMI constant of 16~$mu$J/m$^{2}$ which we independently confirm by Brillouin light scattering. Thickness-dependent measurements reveal that the DMI originates from the oxide interface between the YIG and garnet substrate. The interfacial DMI discovered in the ultrathin YIG films is of key importance for functional chiral magnonics as ultra-low spin-wave damping can be achieved.
Chiral magnetic Mn$_x$Fe$_{1-x}$Ge compounds have an antisymmetric exchange interaction that is tunable with the manganese stoichiometric fraction, $x$. Although millimeter-scale, polycrystalline bulk samples of this family of compounds have been produced, thin-fi
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