Spin waves in a ferromagnetic nanotube of an elliptic cross-section in the presence of a spin-polarized current

Abstract

AbstractIn the paper, spin waves in a ferromagnetic nanotube of an elliptic cross-section in the presence of a spinpolarized electric current are investigated. The linearized Landau-Lifshitz equation in themagnetostatic approximation is used, with the exchange interaction, the dipoledipolemagnetic interaction, the anisotropy effects and the dissipation effects taken into account; the influence of the spin-polarized current is considered by the Slonczewski- Berger term. After elimination of the magnetization density perturbation, an equation for the magnetic potential for the above-described spin excitations is obtained. From this equation, a dispersion relation for spin waves in the nanosystem described previously is obtained. Analysis of the dispersion relation shows that the presence of the spinpolarized current can strengthen or weaken the dissipation, creating an “effective dissipation”; the effect is analogous to the “effective dissipation” in a two-layer ferromagnetic film in the presence of a spin-polarized current. Depending on the direction and the density of the current the spinwave can decay faster or slower than in the absence of the current, transform into a self-sustained wave or grow in amplitude, thus leading to a spin wave generation.