Europhys. Lett.
Volume 68, Number 6, December 2004
Page(s) 888 - 893
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 17 November 2004
Europhys. Lett., 68 (6), pp. 888-893 (2004)
DOI: 10.1209/epl/i2004-10274-6

Scaling of the susceptibility vs. magnetic-field sweep rate in $\chem{Fe_8}$ molecular magnet

M. Jordi1, A. Hernandez-Mínguez1, J. M. Hernandez1, J. Tejada1, S. Stroobants2, J. Vanacken2 and V. V. Moshchalkov2

1  Department de Física Fonamental, Universitat de Barcelona Diagonal 647, 08024 Barcelona, Spain
2  Pulsed Field Group, Laboratory of Solid-State Physics and Magnetism, K.U. Leuven Celestijnenlaan 200D, B-3001 Leuven, Belgium

received 18 August 2004; accepted in final form 14 October 2004
published online 17 November 2004

The dependence of the magnetization reversal on the sweep rate of the applied magnetic field has been studied for single crystals of $\chem{Fe_8}$ magnetic molecules. Our experiments have been conducted at temperatures below 1 $\un{K}$ and sweep rates of the magnetic field between 103 $\un{T/s}$ to 104 $\un{T/s}$. The systematic shift of the values of the magnetic field at which the magnetization reversal occurs, indicates that this reversal process is not governed by the Landau-Zener transition model. Our data can be explained in terms of the superradiance emission model proposed by Chudnovsky and Garanin (Phys. Rev. Lett. 89 (2002) 157201).

75.50.Xx - Molecular magnets.
75.60.Ej - Magnetization curves, hysteresis, Barkhausen and related effects.
42.50.Fx - Cooperative phenomena in quantum optical systems.

© EDP Sciences 2004