RKKY oscillations in the spin relaxation rates of atomic-scale nanomagnets

Exchange interactions with itinerant electrons are known to act as a relaxation mechanism for individual local spins. The same exchange interactions induce the so-called RKKY indirect exchange interaction between two otherwise decoupled local spins. Here, we show that both the spin relaxation and the RKKY coupling can be seen as the dissipative and reactive response to the coupling of the local spins with the itinerant electrons. We thereby predict that the spin relaxation rates of magnetic nanostructures of exchanged coupled local spins, such as nanoengineered spin chains, have an oscillatory dependence on kFd, where kF is the Fermi wave number and d is the interspin distance, very much like the celebrated oscillations in the RKKY interaction. We demonstrate that both T1 and T2 can be enhanced or suppressed, compared to the single-spin limit, depending on the interplay between the Fermi surface and the nanostructure geometrical arrangement. Our results open a route to engineer spin relaxation and decoherence in atomically designed spin structures.J.F.R. acknowledges financial supported by MEC-Spain (Grant No. FIS2013-47328-C2-2-P) and Generalitat Valenciana (Grant No. ACOMP/2010/070), Prometeo. This work is funded by ERDF funds through the Portuguese Operational Program for Competitiveness and InternationalizationÐ COMPETE 2020, and National Funds through FCT-The Portuguese Foundation for Science and Technology, under the project PTDC/FIS-NAN/4662/2014 (Project. No. 016656). F.D. acknowledges support from Spanish Government through Grant No. MAT2015-66888-C3-2-R and Basque Government, Grant No. IT986-16.Peer Reviewe