Oblique propagation of longitudinal spin-electron acoustic waves under the influence of the Coulomb exchange interaction and the quantum Bohm potential

Influence of the exchange interaction on the properties of the spin-electron acoustic waves at the oblique propagation of waves relatively to the external magnetic field in the magnetically ordered metals is studied. The spectra of the Langmuir wave and the Trivelpiece-Gould wave are also considered. It is well-known that there are two branches of spectrum of the spin-electron acoustic waves in this regime. Change their properties under influence of the exchange interaction is studied. The quantum Bohm potential is included either. The exchange interaction and quantum Bohm potential gives opposite contributions, but they do not compensate each other since they have different dependence on the wave vector. This competition creates a non-monotonical behavior of the Trivelpiece-Gould wave spectrum. The concavity changes in the monotonic spectra of the Langmuir wave and the SEAWs are found.
Comment: 8 pages, 8 figures