Title :
Algorithm for the computation of the FC and ZFC magnetization curves for nanoparticle systems
Author :
Papusoi, C., Jr. ; Stancu, Alexandru ; Papusoi, C. ; Dormann, J.L. ; Nogues, M. ; Tronc, E.
Author_Institution :
Fac. of Phys., Alexandru Ioan Cuza Univ., Iasi, Romania
fDate :
7/1/1998 12:00:00 AM
Abstract :
A new model for the FC and ZFC magnetization processes for fine particle systems is described that uses the two-level model for the thermal relaxation. An approximate method for the resolution of the master equation for a temperature or field varying process is developed. The volume and easy axis distributions as well as the temperature dependencies of the intrinsic magnetization and anisotropy are taken into account. In the low applied field limit and for randomly oriented systems, an Onsager-type attempt shows that dipole interactions can account for the dependence of the FC and ZFC magnetization curves on the concentration and sample shape. Numerical results are in good agreement with experimental data obtained for various concentration γ-Fe2O3 nanoparticle systems
Keywords :
iron compounds; magnetic anisotropy; magnetic particles; magnetic relaxation; magnetisation; master equation; nanostructured materials; superparamagnetism; γ-Fe2O3 nanoparticle systems; FC magnetization curves; Fe2O3; Onsager-type attempt; ZFC magnetization curves; algorithm; anisotropy; dipole interactions; easy axis distributions; fine particle systems; intrinsic magnetization; low applied field limit; master equation; model; nanoparticle systems; randomly oriented systems; temperature dependencies; thermal relaxation; two-level model; Anisotropic magnetoresistance; Cooling; Energy barrier; Equations; Magnetic field measurement; Magnetic moments; Magnetization; Shape measurement; Temperature dependence; Thigh;
Journal_Title :
Magnetics, IEEE Transactions on
