Thermally activated and field-tuned tunneling in Mn12Ac studied by ac magnetic susceptibility

F. Luis*, J. Bartolomé, J. F. Fernández, J. Tejada, J. M. Hernández, X. X. Zhang, R. Ziolo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

153 Scopus citations

Abstract

The magnetic ac susceptibility χ of oriented Mn12Ac crystallites has been measured as a function of temperature, field, and frequency. The field has been applied at different values of the angle θ with respect to the sample easy axis. For T= 5 K, the isothermal and adiabatic χ limits have been determined as a function of field. For θ=0° and intermediate frequencies, Lorentzian-shaped peaks have been observed at magnetic field values Hn=nH1 with n=0, 1, and 2 where H1=4.1 kOe. As θ increases these maxima shift to higher fields, that satisfy Hncosθ=const, and decrease in amplitude. The relaxation time τ1 follows Arrhenius' law with respect to temperature and decreases sharply at H=Hn. The observed phenomenology unambiguously proves the existence of field-tuned tunneling between excited magnetic states which are thermally populated. At 5 K, the effective activation energy and the spin states involved in the tunneling process have been obtained.

Original languageEnglish (US)
Pages (from-to)11448-11456
Number of pages9
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume55
Issue number17
StatePublished - May 1 1997
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics

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