Eur. Phys. J. B 24, 291-295 (2001)
https://doi.org/10.1007/s10051-001-8676-3

Damage processes in Fe₃O₄ magnetic insulator irradiated by swift heavy ions. Experimental results and modelisation

¹ GPM (UMR 6634) , CNRS-Université de Rouen, 76821 Mont-Saint-Aignan Cedex, France
² CRISMAT (UMR 6508) , ISMRA, 14050 Caen Cedex, France
³ Laboratoire des Solides Irradiés, École Polytechnique, Route de Saclay, 91128 Palaiseau, France

Corresponding author: ^a abdeslem.fnidiki@univ-rouen.fr

Received: 18 April 2001
Revised: 24 July 2001
Published online: 15 December 2001

Abstract

The behavior of the magnetic properties of magnetite Fe₃O₄ irradiated by swift heavy ions is investigated by magnetization measurements. Although there is no induced structural phase transformation, both coercive field and saturation magnetization are sensitive to ion irradiation and exhibit different behaviors depending on the ion fluence range. In the low fluence regime, the coercive field increases, which is evidence for a strong pinning of magnetic domain boundaries by the induced defects. The magnetization shows a decrease in the saturation value and tends to reorient perpendicularly to the ion track axis. At high fluence, the initial magnetic properties of the sample are nearly restored. The changes in the magnitude and the direction of magnetization are interpreted by magnetostrictive effects related to the stress induced by irradiation. A phenomenological model is applied to reproduce the fluence evolution of the saturation magnetization, assuming relaxation of the stress induced around the core of defects of the tracks by overlapping effects at high fluence. The results are compared to those obtained in the case of yttrium iron garnet Y₃Fe₅O₁₂.