The energy splitting of the low-lying levels has been investigated on two magnetic molecular clusters Fe-6 and Fe-10 by means of low-temperature zero-field specific-heat measurements. Significant deviations from the usual C similar to T-2 law were observed above the maximum of the main Schottky anomalies as a result of nonnegligible contributions from the excited spin states with S>1 and the estimated lattice contributions follow a phenomenological power law C/R similar to T-alpha with alpha-2.7 for both these compounds. The singlet-triplet energy gaps evaluated by the Schottky anomaly, T-0=19.2 K for Fe6 and 4.56 K for Fe-10, are smaller than what we can estimate by a simplified spin-Hamiltonian approach in the strong exchange approximation and using the energy levels obtained by the high-field magnetization and susceptibility measurements. This discrepancy asks for a more complex description of the low-lying states of these molecular clusters, beyond the strong exchange approximation. At very low temperatures T<<1 K, two low-energy Schottky anomalies were also observed in Fe-10, probably due to a small fraction of defected rings or to hyperfine contributions.

Low-temperature specific heat of Fe-6 and Fe-10 molecular magnets / Affronte, Marco; Lasjaunias, Jc; Cornia, Andrea; Caneschi, A.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - STAMPA. - 60:(1999), pp. 1161-1166.

Low-temperature specific heat of Fe-6 and Fe-10 molecular magnets

AFFRONTE, Marco;CORNIA, Andrea;
1999

Abstract

The energy splitting of the low-lying levels has been investigated on two magnetic molecular clusters Fe-6 and Fe-10 by means of low-temperature zero-field specific-heat measurements. Significant deviations from the usual C similar to T-2 law were observed above the maximum of the main Schottky anomalies as a result of nonnegligible contributions from the excited spin states with S>1 and the estimated lattice contributions follow a phenomenological power law C/R similar to T-alpha with alpha-2.7 for both these compounds. The singlet-triplet energy gaps evaluated by the Schottky anomaly, T-0=19.2 K for Fe6 and 4.56 K for Fe-10, are smaller than what we can estimate by a simplified spin-Hamiltonian approach in the strong exchange approximation and using the energy levels obtained by the high-field magnetization and susceptibility measurements. This discrepancy asks for a more complex description of the low-lying states of these molecular clusters, beyond the strong exchange approximation. At very low temperatures T<<1 K, two low-energy Schottky anomalies were also observed in Fe-10, probably due to a small fraction of defected rings or to hyperfine contributions.
1999
60
1161
1166
Low-temperature specific heat of Fe-6 and Fe-10 molecular magnets / Affronte, Marco; Lasjaunias, Jc; Cornia, Andrea; Caneschi, A.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - STAMPA. - 60:(1999), pp. 1161-1166.
Affronte, Marco; Lasjaunias, Jc; Cornia, Andrea; Caneschi, A.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/7731
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