Evidences of non-Arrhenius magnetic relaxation in macroscopic systems: Experiments and related simulations

¹ Laboratoire de Magnetisme Lois Néel-CNRS, 25 Avenue des Martyrs, 38042 Grenoble Cedex 9, France
² Departamento de Física de la Materia Condensada, ICMA Universidad de Zaragoza-CSIC, Pedro Cerbuna 12, 50009 Zaragoza, Spain
³ Laboratoire d'Acustique et d'Optique de la Matiére Condensée, Université Pierre et Marie Curie, 75252 Paris cedex 05, France
⁴ Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain

Received: 22 August 1997
Accepted: 29 January 1998

Abstract

We report on the time evolution of the magnetization measured under constant applied field in highly homogeneous amorphous CoZrDy thin films. Our results show that the thermally activated reversal proceeds after a time interval (waiting time) whose magnitude depends on the field value and during which the macroscopic state of the sample evolves very slowly. Also, and differently from the relaxation of systems having distributed properties, the observed reversal is accomplished in a finite time interval. The experimental data are adequately reproduced by the relaxation of a 2D micromagnetic model which clearly suggests that the thermally activated reversal takes place through a nucleation-propagation sequence also showing some indications of collective behavior.