arXiv subjects

Anna Maria Friedel

Publications and source records attributed to Anna Maria Friedel.

3 recordsLinked to original sources

arXiv2026

Magneto-optical signal from $\mathrm{Co_2Mn}$-based Heusler thin films in MOKE and BLS

$\mathrm{Co_2Mn}$-based Heusler compounds offer a versatile, composition-tunable platform for magnonics and spintronics. Among them, the half-metallic $\mathrm{Co_2MnSi}$ is of particular interest for magnonics owing to its ultralow Gilbert damping, yet its weak magneto-optical response in the visible challenges optical probing such as Brillouin light scattering (BLS). We study the magneto-optical response of epitaxial $\mathrm{Co_2Mn}X$ films ($X = \{\mathrm{Al}_x\mathrm{Si}_{1-x}, \mathrm{Ga}_x\mathrm{Ge}_{1-x}, \mathrm{Sn}\}$) by magneto-optical Kerr effect (MOKE) spectroscopy and BLS. Angle-resolved MOKE resolves a significant, wavelength-dependent quadratic MOKE (QMOKE) only for $\mathrm{Co_2MnSi}$, whereas $\mathrm{Co_2MnAl}$, $\mathrm{Co_2MnGa}$ and $\mathrm{Co_2MnSn}$ respond dominantly linearly. Comparing BLS intensities of thermal magnons at two wavelengths, $\mathrm{Co_2MnSi}$ gives the weakest signal at 532 nm yet among the strongest at 457 nm, tracking the spectral dependence of its Kerr angle. These results emphasise the relation between the two magneto-optical techniques, guiding the choice of probing wavelength for $\mathrm{Co_2Mn}$-based Heusler compounds.

cond-mat.mes-hall↗

arXiv2026

Spin-polarization of the electric current in half-metallic Co$_2$MnSi Heusler thin films

Using propagating spin wave spectroscopy we measure the spin wave Doppler shift in patterned MgO/Co$_2$MnSi/MgO thin films and determine the degree of spin-polarization of the electric current. Our measurements reveal that the current is fully spin-polarized in the devices. This shows that the half-metallic character of the electron band structure translates into a fully spin polarized current flowing across the patterned films. Additionally, we measure a current-induced change of the spin-wave attenuation from which we estimate the non-adiabatic spin-transfer-torque parameter.

cond-mat.mtrl-sci↗

arXiv2026

Epitaxial $\mathrm{Co_2MnSi}$ with intrinsic magnetocrystalline anisotropy as a route to bias-field-free nonlinear half-metal magnonics at the nanoscale

Half-metallic Heusler compounds like $\mathrm{Co_2MnSi}$ allow to bridge magnonic and spintronic functionality for hybrid unconventional computing approaches with sought-after properties like 100% spin polarization and associated low Gilbert damping $\alpha\leq 10^{-3}$. However, the desirable material parameters are inherently tied to the crystal lattice with a particularly critical dependence on structural order in $\mathrm{Co_2MnSi}$. To date, the successful fabrication of nanoscale devices with robust structural integrity remains yet a challenge, and consequently the impact of the material parameters on the resulting nonlinear spin-wave dynamics remains largely unexplored. Here, we report on a study of linear and nonlinear spin-wave dynamics in transversally magnetized $\mathrm{Co_2MnSi}$ waveguides with impeccable crystalline ordering. We show that epitaxial, $\mathrm{L2}_1$-ordered $\mathrm{Co_2MnSi}$ exhibits an intrinsic cubic anisotropy with first- and second-order contributions, stabilizing a magnetization alignment along the crystal $\langle110\rangle$ directions. We confirm the implication of an unaffected crystal structure resulting in preserved magnetic properties in the patterned structures. Herein, the persistent magnetocrystalline anisotropy reshapes the spin-wave dispersion which yields a first-order nonlinear instability suppression range extending over several GHz - even for vanishing bias fields. Moreover, the intrinsic magnetocrystalline anisotropy can be exploited to counteract shape demagnetization for a stabilized low bias field operation in the favourable Damon-Eshbach geometry with high group velocities and decay lengths. Together with the proven half-metallicity and ultralow Gilbert damping, this research establishes $\mathrm{Co_2MnSi}$ as a robust, scalable platform towards bias-field-free nonlinear half-metal magnonics.

cond-mat.mes-hall↗