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Tunneling of a large spin via hyperfine interactions

D. A. Garanin·E. M. Chudnovsky·R. Schilling
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Abstract

We consider a large spin \bf S in the magnetic field parallel to the uniaxial crystal field, interacting with N >> 1 nuclear spins \bf I_i via Hamiltonian \cal H = -DS_z^2 - H_zS_z+ A{\bf S}\cdot \sum_{i=1}^N {\bf I}_i with A << D, at temperature T. Tunneling splittings and the selection rules for the resonant values of H_z are obtained perturbatively. The quantum coherence exists at T << ASI while at T >= ASI the coherence is destroyed and the relaxation of \bf S is described by a stretched dependence which can be close to log t under certain conditions. Relevance to Mn-12 acetate is discussed.

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D. A. Garanin, E. M. Chudnovsky, R. Schilling. 1999-11-04. Tunneling of a large spin via hyperfine interactions. https://doi.org/10.1103/physrevb.61.12204

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