Modelling compensated antiferromagnetic interfaces with MuMax3

We show how compensated antiferromagnetic spins can be implemented in the micromagnetic simulation program MuMax3. We demonstrate that we can model spin flop coupling as a uniaxial anisotropy for small canting angles and how we can take into account the exact energy terms for strong coupling between a ferromagnet and compensated antiferromagnet. We also investigate the training effect in biaxial antiferromagnets and reproduce the training effect in a polycrystalline IrMn/CoFe bilayer.Comment: 11 pages + Supplementary Material (10 pages

Magnetic dot arrays modeling via the system of the radial basis function networks

Two dimensional square lattice general model of the magnetic dot array is introduced. In this model the intradot self-energy is predicted via the neural network and interdot magnetostatic coupling is approximated by the collection of several dipolar terms. The model has been applied to disk-shaped cluster involving 193 ultrathin dots and 772 interaction centers. In this case among the intradot magnetic structures retrieved by neural networks the important role play single-vortex magnetization modes. Several aspects of the model have been understood numerically by means of the simulated annealing method.Comment: 16 pages, 8 figure

Computer simulation of a thin magnetic film with vertical anisotropy

We describe a discrete micromagnetic model for a thin magnetic layer which has been developed to perform computer simulations of the system. The magnetisation in this model is given in terms of a cubic array of interacting microscopic spins. The dynamics of the spins is given by a time discretisation of the Landau-Lifshitz-Gilbert equations of motion. The array is continued periodically in the x- and y-direction in order to reduce boundary effects, and is finite in the z-direction. The mutual interactions that are incorporated are exchange and dipole interaction, and the crystal lattice interaction is modeled by a roughly vertical uniaxial anisotropy term. The strengths of the different interactions are scaled so as to conform to values for CoCr, fitted to experimental results within the context of continuum models. For this setup we have determined full hysteresis curves and compared with experimental results of these films

Parametric optimization for terabit perpendicular recording

The design of media for ultrahigh-density perpendicular recording is discussed in depth. Analytical and semianalytical models are developed to determine the constraints upon the media to fulfill requirements of writability and thermal stability, and the effect of intergranular exchange coupling is examined. The role of vector fields during the write process is examined, and it is shown that one-dimensional models of perpendicular recording have significant deficiencies. A micromagnetic model is described and the results of simulations of recording undertaken with the model are presented. The paper demonstrates that there is no physical reason why perpendicular recording should not be possible at or above 1 Tb/in(2)

Numerical study of magnetic processes: extending the Landau-Lifshitz-Gilbert approach from nanoscale to microscale

The micromagnetic theory describes the magnetic processes in magnetic materials on a microscopic time and space length. Therefore, micromagnetic models are since long employed in the design of for instants magnetic storage media as magnetic tapes and Random Access Memory elements, used in computers. The use of efficient numerical techniques and the availability of powerful computers now make it possible to apply the same micromagnetic models on larger and more complex material systems with the aim of increasing our insight in the experimentally observed magnetic phenomena. In this PhD research, an efficient numerical micromagnetic model is developed that enables the analysis of magnetic processes starting from the nanometer space scale up to the micrometer space scale. Therefore, efficient algorithms are presented on the one hand to simulate the ultra fast dynamics of the magnetic processes as described by the Landau-Lifshitz-Gilbert equation. On the other hand, powerful numerical techniques are developed to evaluate the magnetic fields, characteristic to the micromagnetic description, in a fast way. The developed micromagnetic model is validated extensively in comparative studies with other micromagnetic and macroscopic magnetic material models. Moreover, the model is successfully applied in different magnetic research domains: magnetic switching processes in classical samples with nanometer dimensions are analysed, magnetic domains are studied in structures with order micrometer dimensions and magnetic hysteresis properties are investigated

MAGNETISATION REVERSAL AND DOMAIN STRUCTURE IN THIN MAGNETIC FILMS: THEORY AND COMPUTER SIMULATION

A model is introduced for the theoretical description of nanoscale magnetic films with high perpendicular anisotropy. In the model the magnetic film is described in terms of single domain magnetic grains, interacting via exchange as well as via dipolar forces. Additionally, the model contains anisotropy energy and a coupling to an external magnetic field. Disorder is taken into account in order to describe realistic domain and domain wall structures. Within this framework the dependence of the energy on the film thickness can be discussed. The influence of a finite temperature as well as the dynamics can be modeled by a Monte Carlo simulation. The results on the hysteresis loops, the domain configurations, and the dynamics during the reversal process are in good agreement with experimental findings.Comment: 4 Pages, Postscript, uuencode