Dynamic unidirectional anisotropy in cubic FeGe with antisymmetric spin-spin-coupling

Abstract

We report strong unidirectional anisotropy in bulk polycrystalline B20 FeGe measured by ferromagnetic resonance spectroscopy. Bulk and micron sized samples were produced and analytically characterized. FeGe is a B20 compound with inherent Dzyaloshinskii-Moriya interaction. Lorenz microscopy confirms a skyrmion lattice at 190 K in a magnetic field of 150 mT. Ferromagnetic resonance was measured at 276 K ± 1 K, near the Curie temperature. Two resonance modes were observed, both exhibit a unidirectional anisotropy of K = 1153 J/m 3 ± 10 J/m 3 in the primary, and K = 28 J/m 3 ± 2 J/m 3 in the secondary mode, previously unknown in bulk ferromagnets.Additionally, about 25 standing spin wave modes are observed inside a micron sized FeGe wedge, measured at room temperature (∼ 293 K). These modes also exhibit unidirectional anisotropy.

Confined dipole and exchange spin waves in a bulk chiral magnet with Dzyaloshinskii-Moriya interaction

“…1 (a)] so that the spin waves propagating along opposite directions at the same frequency own different k. The discrepancy in k does not allow for the conventional standing spin waves. Numerical methods showed involved spin waves phase profiles in nanoscale magnets with DMI [32][33][34]. In thin films of the * dirk.grundler@epfl.ch chiral magnet FeGe, an oscillating factor exp(−iQz) was introduced when the ferromagnetic resonance (FMR) at k = 0 and perpendicular standing spin waves with finite k were interpreted, where Q is the pitch vector in a chiral magnet [35].…”