Intrinsic magnetic resonance in nanoparticles: Landau damping in the collisionless regime

Abstract In a uniaxially anisotropic particle the frequency of intrinsic ferromagnetic resonance depends on the angle deviation of the magnetic moment from its equilibrium position. At low spin–lattice relaxation and in the presence of superparamagnetism, the regime of relaxation in an assembly of such particles closely resembles the Landau damping regime, which is well known in the kinetic theory of plasma. In the high-temperature limit in the case of polydisperse systems, particle volume and surface anisotropy affect the absorption lines differently.