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/m3 10 \; J/m3 in the primary, and K=28 \; J/m3 2 \; J/m3 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.