Quadrupole spin oscillations in polarized rarefied media.
A new branch of weakly damped collective magnetic excitations in spin-polarized low-density systems is predicted. This type of wave corresponds to the transverse oscillations of the macroscopic quadrupole moment while the magnetization does not oscillate. The spectra of both spin waves and quadrupole modes are calculated. The theory can be applied to gaseous H↓, D↓, and other rarefied gases of S=1 particles