Thermodynamics and spin-tunneling dynamics in ferric wheels with excess spin

Florian Meier and Daniel Loss
Phys. Rev. B 64, 224411 – Published 20 November 2001
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Abstract

We study theoretically the thermodynamic properties and spin dynamics of a class of magnetic rings closely related to ferric wheels, antiferromagnetic ring systems, in which one of the Fe (III) ions has been replaced by a dopant ion to create an excess spin. Using a coherent-state spin path integral formalism, we derive an effective action for the system in the presence of a magnetic field. We calculate the functional dependence of the magnetization and tunnel splitting on the magnetic field and show that the parameters of the spin Hamiltonian can be inferred from the magnetization curve. We study the spin dynamics in these systems and show that quantum tunneling of the Néel vector also results in tunneling of the total magnetization. Hence, the spin correlation function shows a signature of Néel vector tunneling, and electron spin resonance (ESR) techniques or ac susceptibility measurements can be used to measure both the tunneling and the decoherence rate. We compare our results with exact diagonalization studies on small ring systems. Our results can be easily generalized to a wide class of nanomagnets, such as ferritin.

  • Received 2 July 2001

DOI:https://doi.org/10.1103/PhysRevB.64.224411

©2001 American Physical Society

Authors & Affiliations

Florian Meier and Daniel Loss

  • Department of Physics and Astronomy, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland

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Issue

Vol. 64, Iss. 22 — 1 December 2001

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