Proton spin-lattice relaxation induced by quantum tunneling of the magnetization in the molecular nanomagnet Fe8

Y. Furukawa, K. Aizawa, K. Kumagai, R. Ullu, A. Lascialfari, and F. Borsa
Phys. Rev. B 69, 014405 – Published 9 January 2004
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Abstract

We report the observation of the effect of the quantum tunneling of the magnetization in the molecular nanomagnet [Fe8(N3C6H15)6O2(OH)12][Br89H2O] (in short, Fe8) on the proton spin-lattice relaxation rates (T11) measured in single crystal Fe8 at 1.5 K. When the external field is applied parallel to the magnetic easy axis of the molecular nanomagnet, T11 decreases monotonically, a behavior well explained in terms of the magnetization fluctuations due to spin-phonon interaction. On the other hand, a peak of T11 is observed as a function of transverse field for a value of H in the range 2.5–3.5 T. The position and shape of the peak depend upon the orientation of the field in the hard plane and the peak disappears as soon as a small out-of-plane magnetic-field component is introduced by misaligning the crystal. The experimental observations can be explained by considering the effect of the transverse field on the tunneling splitting whereby the peak of T11 is a direct consequence of the matching condition of the incoherent tunneling probability with the proton Larmor frequency.

  • Received 9 October 2003

DOI:https://doi.org/10.1103/PhysRevB.69.014405

©2004 American Physical Society

Authors & Affiliations

Y. Furukawa, K. Aizawa, and K. Kumagai

  • Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan

R. Ullu and A. Lascialfari

  • Dipartimento di Fisica “A Volta” e Unita’INFM di Pavia, Via Bassi 6, I27100 Pavia, Italy

F. Borsa

  • Department of Physics and Astronomy, Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
  • Dipartimento di Fisica “A Volta” e Unita’INFM di Pavia, Via Bassi 6, I27100 Pavia, Italy

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Issue

Vol. 69, Iss. 1 — 1 January 2004

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