Y. Roussigné

Interfacial Dzyaloshinskii-Moriya interaction in perpendicularly-magnetized Pt/Co/AlO

Spin waves in perpendicularly magnetized

_x

{\text{Pt/Co/AlO}}_{x}/\text{Pt}

ultrathin films measured by Brillouin light spectroscopy

ultrathin films with varying Co thicknesses (0.6--1.2 nm) have been studied with Brillouin light spectroscopy in the Damon-Eshbach geometry. The measurements reveal a pronounced nonreciprocal propagation, which increases with decreasing Co thickness. This nonreciprocity, attributed to an interfacial Dzyaloshinskii-Moriya interaction (DMI), is significantly stronger than asymmetries resulting from surface anisotropies for such modes. Results are consistent with an interfacial DMI constant

Probing the Dzyaloshinskii-Moriya interaction in CoFeB ultrathin films using domain wall creep and Brillouin light spectroscopy

{D}_{\mathrm{s}}=\ensuremath{-}1.7\ifmmode\pm\else\textpm\fi{}0.11\phantom{\rule{0.28em}{0ex}}\text{pJ}

Elastic properties of β-SiC films by Brillouin light scattering

/m, which favors left-handed chiral spin structures. This suggests that such films below 1 nm in thickness should support chiral states such as skyrmions at room temperature.

Magnetization pinning in conducting films demonstrated using broadband ferromagnetic resonance

We have characterized the strength of the interfacial Dyzaloshinskii-Moriya interaction (DMI) in ultrathin perpendicularly magnetized CoFeB/MgO films, grown on different underlayers of W, TaN, and Hf, using two experimental methods. First, we determined the effective DMI field from measurements of field-driven domain wall motion in the creep regime, where applied in-plane magnetic fields induce an anisotropy in the wall propagation that is correlated with the DMI strength. Second, Brillouin light spectroscopy was employed to quantify the frequency non-reciprocity of spin waves in the CoFeB layers, which yielded an independent measurement of the DMI. By combining these results, we show that DMI estimates from the different techniques only yield qualitative agreement, which suggests that open questions remain on the underlying models used to interpret these results.

Velocity asymmetry of Dzyaloshinskii domain walls in the creep and flow regimes

Brillouin light scattering has been used to investigate elastic properties of a monocrystalline and of 〈111〉 textured polycrystalline 3C polytype silicon carbide films that have been deposited on silicon substrate by chemical vapor deposition. Taking advantage from the detection of different acoustic modes, a complete elastic characterization of the films has been achieved. The three unknown elastic constants of the monocrystalline 3C-SiC, namely, c11=395 GPa, (c11−c12)/2=136 GPa, and c44=236 GPa have been selectively determined, respectively, from the frequency of the longitudinal and of the shear horizontal bulk modes traveling parallelly to the film surface. These determinations are in agreement with the frequency of the observed Rayleigh surface mode, of the pseudosurface mode, and of the bulk waves propagating at different angles from the normal of the single crystal film plane and consistent with existing theoretical calculations of β-SiC elastic constants. Finally, the calculated Voigt average valu...

Spin waves in magnetic wires:: a Brillouin study

The broadband microstrip ferromagnetic resonance (FMR), cavity FMR, and Brillouin light scattering spectroscopy techniques have been applied for detection and characterization of a magnetic inhomogeneity in a film sample. In the case of a 100 nm thick permalloy film, an additional magnetically depleted top sublayer has been detected due to pinning effect it produces on the magnetization in the bulk of the film. The pinning results in appearance of an exchange standing spin wave mode in the broadband FMR absorption spectrum, whose amplitudes are different depending on whether the film or the film substrate faces the microstrip transducer. Comparison of the experimental amplitudes for this mode with results of our theory for both film placements revealed that the depleted layer is located at the film surface facing away from the film substrate. Subsequent broadband FMR characterization of a large number of other presumably single-layer films with thicknesses in the range 30–100 nm showed the same result.

High frequency magnetic excitations in patterned NiFe∕Cu∕NiFe trilayered stripes subjected to a transverse magnetic field

We have carried out measurements of domain wall dynamics in a Pt/Co/GdOx(t) wedge sample with perpendicular magnetic anisotropy. When driven by an easy-axis field Hz in the presence of an in-plane field Hx, the domain wall propagation is different along [Formula: see text]x, as expected for samples presenting Dzyaloshinskii-Moriya (DMI) interaction. In the creep regime, the sign and the value of the domain wall velocity asymmetry changes along the wedge. We show that in our samples the domain wall speed versus Hx curves in the creep regime cannot be explained simply in terms of the variation of the domain wall energy with Hx, as suggested by previous works. For this reason the strength and the sign of the DMI cannot be extracted from these measurements. To obtain reliable information on the DMI strength using magnetic field-induced domain wall dynamics, measurements have been performed with high fields, bringing the DW close to the flow regime of propagation. In this case we find large values of the DMI, consistent in magnitude and sign with those obtained from Brillouin light scattering measurements.

Spin waves in a magnetic stripe submitted to a perpendicular magnetic field

Abstract A detailed Brillouin light scattering study of the dispersion of surface spin waves in cobalt wires is reported. A comparison with the dispersion curve of the unpatterned continuos film is achieved and the effects of the size-dependent demagnetizing field are discussed. Concerning the pseudo-bulk modes appearing in the patterned film, as expected, their variation is quasi-independent from the variation of the angle of incidence. The experimental Brillouin spectra do not display any splitting of the Damon–Eshbach mode into a set of discrete lines in contrast with previously published results on permalloy. We interpret this difference as arising from the large experimental linewidth combined with the presence of an anisotropy in the case of cobalt. A qualitative model of the scattering intensity is presented in order to illustrate this difference. The involved eigenfrequencies are derived from numerical calculations which also allow us to discuss the relevant quantization conditions of the in-plane wave vector.