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Your search keyword '"Pini, M"' showing total 32 results
Start Over Author "Pini, M" Journal physical review b
32 results on '"Pini, M"'

5. In-plane rotation of magnetic stripe domains inFe1−xGaxthin films

Author

Fin, S., primary, Tomasello, R., additional, Bisero, D., additional, Marangolo, M., additional, Sacchi, M., additional, Popescu, H., additional, Eddrief, M., additional, Hepburn, C., additional, Finocchio, G., additional, Carpentieri, M., additional, Rettori, A., additional, Pini, M. G., additional, and Tacchi, S., additional

Published
2015
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32. Proton NMR study of spin dynamics in the magnetic organic chains M(hfac)3 NITEt (M=Eu3+,Gd3+).

Author

Mariani, M., Lascialfari, A., Caneschi, A., Ammannato, L., Gatteschi, D., Rettori, A., Pini, M. G., Cucci, C., and Borsa, F.

Subjects
*MAGNETIC resonance microscopy, *MAGNETIC coupling, *PHASE transitions
Abstract

In this work, we present a nuclear magnetic resonance (NMR) study of the spin dynamics in the rare-earth-based low-dimensional molecular magnetic chains Eu(hfac)3NITEt and Gd(hfac)3NITEt (in short, Eu-Et and Gd-Et). Although both samples are based on the same chemical building block, [(hfac)3NITEt], their magnetic properties change dramatically when the Eu3+ ion, which is nonmagnetic at low temperatures, is substituted by the magnetic Gd3+ ion. The present proton NMR investigation shows that, down to the lowest investigated temperature (T=1.5 K for Gd-Et and T=3 K for Eu-Et), the Eu-Et chain behaves as a one-dimensional Heisenberg model with antiferromagnetic exchange coupling (J=-20 K) between s=1/2 organic radicals, and has a T-independent exchange frequency (ωe=2.6?1012 rad/s). In the Gd-Et chain, in contrast, a competition arises between nearest-neighbor ferromagnetic coupling and next-nearest-neighbor antiferromagnetic coupling; moreover, two phase transitions have previously been found, in agreement with Villain's conjecture: a first transition, at T0=2.2 K, from a high temperature paramagnetic phase to a chiral spin liquid phase, and a second transition, at TN=1.9 K, to a three-dimensional helical spin solid phase. Contrary to the Eu-Et chain (whose three-dimensional ordering temperature is estimated to insurge at very low, TN≈0.3 K), critical spin dynamics effects have been measured in the Gd-Et chain on approaching TN=1.9 K: namely, a divergence of the proton nuclear spin-lattice relaxation rate 1/T1, which in turn produces a sudden wipe-out of the NMR signal in a very narrow (ΔT~0.04 K) temperature range above TN. Below TN, an inhomogeneous broadening of the NMR line indicates a complete spin freezing. At T0=2.2 K, instead, such critical effects are not observed because NMR measurements probe the two-spin correlation function, while the chiral spin liquid phase transition is associated with a divergence of the four-spin correlation function. [ABSTRACT FROM AUTHOR]

Published
2016
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