Micromagnetic simulation of a ferromagnetic particle

In this work, the magnetic behaviour of a ferromagnetic particle has been investigated by means of micromagnetic modelling, using the Finite Element Method. The simulations were performed on an ellipsoidal particle with uniaxial magnetocrystalline anisotropy by varying the anisotropy constant, the shape and dimensions of the particle. The results indicate the critical particle size for different reversal modes. Above a critical size the formation and motion of domain walls is clearly observed. The associated nucleation and coercive fields are estimated from the demagnetization curves

A New Approach to Include Surface Contributions in Micromagnetic Simulations of Nanoparticles

AbstractIn this work a micromagnetic model is presented for ferromagnetic nanoparticles where the surface is treated as a single effective layer and not as a separate shell. The model consists of two coupled Partial Differential Equations (PDE), one for the magnetization vector of the bulk volume and the second for the outer nodes. The strength of the coupling depends on the effective width of the layer. Simulations were made by means of the Finite Element Method (FEM). For a comparison FEM for core/shell type and atomistic Monte Carlo simulations were also performed. Our results show that Hs, the field where reversal takes place, varies as ∼1/D, where D is the particle's radius, with the anisotropy strength for any anisotropy direction. Moreover the computational cost of the effective layer model is lower than the core shell one, thus can be easily extended to larger particles where dipolar interactions should also be taken into account