Local spin dynamics in magnetic molecular chains studied by NMR and μSR

We present NMR and MUSR study of spin dynamics in one-dimensional and quasi-one-dimensional molecular magnets of recent synthesis. In particular, we focus on the so called Gd(hfac)3NIT-R and CoPhOMe magnetic chains families. For Gd-R helimagnets we show some differences between ‘‘weakly frustrated systems’’ and ‘‘fully frustrated systems’’. The different behaviour is due to the different radical inserted in the chains (R = Me, Ph for ‘‘weakly frustrated systems’’ and R = iPr, Et for ‘‘fully frustrated systems’’). The existence of different phase transitions, particularly to 3D long-range magnetic order in Gd-Ph and to chiral order in Gd-iPr, is remarked together with a comparison between results obtained from macroscopic and microscopic investigating techniques. As regards CoPhOMe slowly relaxing chain, the 1H NMR measurements confirm the freezing of the spins at low temperature, which prevents the 3D long-range order, and display the presence of two relaxation mechanisms related to distinct contributions to the local spin relaxation.