Magnetic properties and hyperfine interactions in Cr-8, Cr7Cd, and Cr7Ni molecular rings from F-19-NMR

作者：Bordonali L^*; Garlatti E; Casadei C M; Furukawa Y; Lascialfari A; Carretta S; Troiani F; Timco G; Winpenny R E P; Borsa F

来源：Journal of Chemical Physics, 2014, 140(14): 144306.

DOI：10.1063/1.4870469

A detailed experimental investigation of the F-19 nuclear magnetic resonance is made on single crystals of the homometallic Cr-8 antiferromagnetic molecular ring and heterometallic Cr7Cd and Cr7Ni rings in the low temperature ground state. Since the F- ion is located midway between neighboring magnetic metal ions in the ring, the F-19-NMR spectra yield information about the local electronic spin density and F-19 hyperfine interactions. In Cr-8, where the ground state is a singlet with total spin S-T = 0, the F-19-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the F-19-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S-T = 1. In the heterometallic rings, Cr7Cd and Cr7Ni, whose ground state is magnetic with S-T = 3/2 and S-T = 1/2, respectively, the F-19-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the F-19-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F--Ni2+ and the F--Cd2+ bonds. The values of the hyperfine constants compare well to the ones known for F--Ni2+ in KNiF3 and NiF2 and for F--Cr3+ in K2NaCrF6. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F- ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

• 出版日期2014-4-14