NMR and μ+SR detection of unconventional spin dynamics in Er(trensal) and Dy(trensal) molecular magnets
| Autor: | Alessandro Lascialfari, Eva Lucaccini, Stefano Carretta, Zaher Salman, Lorenzo Sorace, F. Adelnia, Paolo Arosio, Ferdinando Borsa, Manuel Mariani, Samuele Sanna |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
Muon Absorption spectroscopy Relaxation (NMR) 02 engineering and technology Muon spin spectroscopy 021001 nanoscience & nanotechnology 01 natural sciences Magnetic susceptibility Spectral line Crystallography 0103 physical sciences Isostructural 010306 general physics 0210 nano-technology Spin-½ |
| Zdroj: | Physical Review B. 100 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | Measurements of proton nuclear magnetic resonance ($^{1}\mathrm{H}\phantom{\rule{0.16em}{0ex}}\mathrm{NMR}$) spectra and relaxation and of muon spin relaxation (${\ensuremath{\mu}}^{+}\mathrm{SR}$) have been performed as a function of temperature and external magnetic field on two isostructural lanthanide complexes, Er(trensal) and Dy(trensal) [where ${\mathrm{H}}_{3}\mathrm{trensal}=2,{2}^{\ensuremath{'}},{2}^{\ensuremath{'}\ensuremath{'}}\ensuremath{-}\mathrm{tris}\ensuremath{-}(\mathrm{salicylideneimino})\mathrm{triethylamine}$], featuring crystallographically imposed trigonal symmetry. Both the nuclear $1/{T}_{1}$ and muon \ensuremath{\lambda} longitudinal relaxation rates (LRRs) exhibit a peak for temperatures $T$ 30 K, associated to the slowing down of the spin dynamics, and the width of the NMR absorption spectra starts to increase significantly at $T$ \ensuremath{\sim} 50 K, a temperature sizably higher than the one of the LRR peaks. The LRR peaks have a field and temperature dependence different from those previously reported for all molecular nanomagnets. They do not follow the Bloembergen-Purcell-Pound scaling of the amplitude and position in temperature and field and thus cannot be explained in terms of a single dominating correlation time ${\ensuremath{\tau}}_{\mathrm{c}}$ determined by the spin slowing down at low temperature. Further, for $T50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ the spectral width does not follow the temperature behavior of the magnetic susceptibility \ensuremath{\chi}. We suggest, using simple qualitative considerations, that the observed behavior is due to a combination of two different relaxation processes characterized by the correlation times ${\ensuremath{\tau}}_{\mathrm{LT}}$ and ${\ensuremath{\tau}}_{\mathrm{HT}}$, dominating for $T$ 30 K and $T50\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, respectively. Finally, the observed flattening of LRR for $T$ 5 K is suggested to have a quantum origin. |
| Databáze: | OpenAIRE |
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