Spin-wave contributions to nuclear magnetic relaxation in magnetic metals

Abstract:

The longitudinal and transverse nuclear magnetic relaxation rates 1/T ₁(T) and 1/T ₂(T) are calculated for three- and two-dimensional (3D and 2D) metallic ferro- and antiferromagnets (FM and AFM) with localized magnetic moments in the spin-wave temperature region. The contribution of the one-magnon decay processes is strongly enhanced in comparison with the standard T-linear Korringa term, especially for the FM case. For the 3D AFM case this contribution diverges logarithmically, the divergence being cut at the magnon gap ω due to magnetic anisotropy, and for the 2D AFM case as ω^-1. The electron-magnon scattering processes yield T ²ln(T/ω) and T ²/ω^1/2-terms in 1/T ₁ for the 3D AFM and 2D FM cases, respectively. The two-magnon (“Raman”) contributions are investigated and demonstrated to be large in the 2D FM case. Peculiarities of the isotropic 2D limit (where the correlation length is very large) are analyzed.