Magnetic properties and hyperfine interactions in Cr{sub 8}, Cr{sub 7}Cd, and Cr{sub 7}Ni molecular rings from {sup 19}F-NMR

Journal Article · Mon Apr 14 00:00:00 EDT 2014 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4870469· OSTI ID:22253245

Bordonali, L.; Borsa, F. ^[1]; Garlatti, E. ^[2]; Casadei, C. M. ^[1]; Furukawa, Y. ^[3]; Lascialfari, A. ^[1]; Carretta, S. ^[4]; Troiani, F. ^[5]; Timco, G.; Winpenny, R. E. P. ^[6]

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1. Department of Physics, Università di Pavia, I-27100 Pavia (Italy)
2. Department of Physics, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)
3. Department of Physics and Astronomy, Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States)
4. Dipartimento di Fisica e Scienze della Terra, Università di Parma, Viale G. P. Usberti 7/A, 43124 Parma (Italy)
5. S3 Istituto Nanoscienze, Consiglio Nazionale delle Ricerche, I-4100 Modena (Italy)
6. The Lewis Magnetism Laboratory, The University of Manchester, M13 9PL Manchester (United Kingdom)

A detailed experimental investigation of the {sup 19}F nuclear magnetic resonance is made on single crystals of the homometallic Cr{sub 8} antiferromagnetic molecular ring and heterometallic Cr{sub 7}Cd and Cr{sub 7}Ni rings in the low temperature ground state. Since the F{sup −} ion is located midway between neighboring magnetic metal ions in the ring, the {sup 19}F-NMR spectra yield information about the local electronic spin density and {sup 19}F hyperfine interactions. In Cr{sub 8}, where the ground state is a singlet with total spin S{sub T} = 0, the {sup 19}F-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 {sup 19}F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S{sub T} = 1. In the heterometallic rings, Cr{sub 7}Cd and Cr{sub 7}Ni, whose ground state is magnetic with S{sub T} = 3/2 and S{sub T} = 1/2, respectively, the {sup 19}F-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 {sup 19}F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F{sup −}-Ni{sup 2+} and the F{sup −}-Cd{sup 2+} bonds. The values of the hyperfine constants compare well to the ones known for F{sup −}-Ni{sup 2+} in KNiF{sub 3} and NiF{sub 2} and for F{sup −}-Cr{sup 3+} in K{sub 2}NaCrF{sub 6}. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F{sup −} ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

• OSTI ID: 22253245
• Journal Information: Journal of Chemical Physics, Vol. 140, Issue 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANISOTROPY
ANTIFERROMAGNETISM
CADMIUM IONS
CHROMIUM IONS
DENSITY
EXCITED STATES
FLUORINE 19
GROUND STATES
HYBRIDIZATION
INTERACTIONS
MAGNETIC FIELDS
MAGNETIC PROPERTIES
MONOCRYSTALS
NICKEL FLUORIDES
NICKEL IONS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
SATELLITES