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Specific heat and magnetic relaxation of the quantum nanomagnetMn12Ac

Specific heat and magnetic relaxation of the quantum nanomagnetMn12Ac

Authors :
Miguel A. Novak
Andrea Caneschi
Roberta Sessoli
A. M. Gomes
Dante Gatteschi
Source :
Physical Review B. 57:5021-5024
Publication Year :
1998
Publisher :
American Physical Society (APS), 1998.

Abstract

We present specific-heat and ac-susceptibility measurements providing more evidence that magnetic quantum tunneling occurs in ${\mathrm{Mn}}_{12}$Ac spin clusters. The total anisotropy energy barrier determined by fitting an Arrhenius law to the magnetic relaxation time is underestimated when compared to the specific-heat data. The expected magnetic contribution using a quadratic spin Hamiltonian needs higher-order terms to improve the agreement with the experiments, as recently done for electron-paramagnetic-resonance spectra. In addition, another interesting effect was observed in the specific-heat measurements when a dc magnetic field is applied. The extra magnetic contribution due to Zeeman splitting is suppressed below the expected superparamagnetic blocking temperature in the time scale of the measurements.

Details

ISSN :
10953795 and 01631829
Volume :
57
Database :
OpenAIRE
Journal :
Physical Review B
Accession number :
edsair.doi...........1448b1e4f889b7663d809eecf1cc6556
Full Text :
https://doi.org/10.1103/physrevb.57.5021