The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

Abstract

A study of the magnetic behaviour of polycrystalline thin films as a function of their thickness is presented in this work. The grain volume was kept approximately constant in the virtual samples. The model includes the exchange interaction, magneto-crystalline anisotropy, surface anisotropy, boundary grain anisotropy, dipolar interaction, and Zeeman effect. The thickness-dependence of the critical temperature, blocking temperature, and irreversibility temperature are presented. Surface anisotropy exerts a great influence at very low thicknesses, producing a monodomain regime. As the thickness increases, the dipolar interaction produces a coupling in-plane of single domains per grain which favours superparamagnetic states. At higher thicknesses, the effects of the in-plane anisotropy produced by dipolar interaction and surface anisotropy decrease dramatically. As a result, the superparamagnetic states present three-dimensional local anisotropies by the grain.

Magnetic, Optical Properties of Magnetite Nanoparticle Synthesized in Different Parameters

“…The coercivity in S1, S2 and S4 samples increased as particle size decreased, except that S3 has increased coercivity. This observed higher coercivity might be caused by magnetic anisotropy or strong spin interactions in strongly crystalline Fe3O4NPs during spin alignment, agreeing with Agudelo et al [35]. In Figure 7, the FTIR spectra for synthesized Fe3O4 NPs (S4), show two bands at 574.029 and 413.392 cm −1 , which are specific to the Fe-O bond, showing that the Fe3O4NP has a high degree of crystallinity.…”