Eur. Phys. J. B 12, 39-46 (1999)
https://doi.org/10.1007/s100510050974

Dipolar interaction and incoherent quantum tunneling: a Monte Carlo study of magnetic relaxation

¹ Dipartimento di Fisica dell'Università di Firenze and Istituto Nazionale di Fisica della Materia, Largo E. Fermi 2, 50125 Firenze, Italy
² Istituto di Elettronica Quantistica del CNR Via Panciatichi 56/30, 50127 Firenze, Italy
³ Département de Recherche Fondamentale sur la Matière Condensée, CEA Grenoble, 17 avenue des Martyrs, 38054 Grenoble Cedex 9, France
⁴ CRTBT, CNRS, B.P. 166, 38042 Grenoble Cedex 9, France

Corresponding author: ^a cuccoli@fi.infn.it

Received: 9 February 1999
Published online: 15 November 1999

Abstract

We study the magnetic relaxation of a system of localized spins interacting through weak dipole interactions, at a temperature large with respect to the ordering temperature but low with respect to the crystal field level splitting. The relaxation results from quantum spin tunneling but is only allowed on sites where the dipole field is very small. At low times, the magnetization decrease is proportional to as predicted by Prokofiev and Stamp, and at long times the relaxation can be described as an extension of a relaxed zone. The results can be directly compared with very recent experimental data on Fe₈ molecular clusters.