NMR and μ+SR detection of unconventional spin dynamics in Er(trensal) and Dy(trensal) molecular magnets

E. Lucaccini, L. Sorace, F. Adelnia, S. Sanna, P. Arosio, M. Mariani, S. Carretta, Z. Salman, F. Borsa, and A. Lascialfari
Phys. Rev. B 100, 174416 – Published 12 November 2019
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Abstract

Measurements of proton nuclear magnetic resonance (H1NMR) spectra and relaxation and of muon spin relaxation (μ+SR) have been performed as a function of temperature and external magnetic field on two isostructural lanthanide complexes, Er(trensal) and Dy(trensal) [where H3trensal=2,2,2tris(salicylideneimino)triethylamine], featuring crystallographically imposed trigonal symmetry. Both the nuclear 1/T1 and muon λ 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 ∼ 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 τc determined by the spin slowing down at low temperature. Further, for T<50K the spectral width does not follow the temperature behavior of the magnetic susceptibility χ. 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 τLT and τHT, dominating for T < 30 K and T>50K, respectively. Finally, the observed flattening of LRR for T < 5 K is suggested to have a quantum origin.

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  • Received 20 May 2019
  • Revised 10 September 2019

DOI:https://doi.org/10.1103/PhysRevB.100.174416

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

E. Lucaccini1, L. Sorace1,*, F. Adelnia2,†, S. Sanna3, P. Arosio4, M. Mariani2,‡, S. Carretta5, Z. Salman6, F. Borsa2,7, and A. Lascialfari4,2

  • 1Dipartimento di Chimica “U. Schiff” and INSTM RU, Università degli Studi di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy
  • 2Dipartimento di Fisica and INSTM, Università degli Studi di Pavia, 27100 Pavia, Italy
  • 3Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, 40127 Bologna, Italy
  • 4Dipartimento di Fisica “A. Pontremoli” and INSTM, Università degli Studi di Milano, 20133 Milano, Italy
  • 5Dipartimento di Scienze Matematiche, Fisiche e Informatiche and INSTM, Università degli Studi di Parma, 43124 Parma, Italy
  • 6Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
  • 7Department of Physics and Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA

  • *Corresponding author: lorenzo.sorace@unifi.it
  • Present address: Vanderbilt University, Institute of Imaging Science, Nashville, TN 37232, USA.
  • Corresponding author: manuel.mariani@unipv.it

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Issue

Vol. 100, Iss. 17 — 1 November 2019

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