Local spin dynamics in magnetic molecular chains studied by NMR and mu SR

We present NMR and mu+SR 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)(3)NIT-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 1 H 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. (c) 2007 Elsevier B.V. All rights reserved.