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A method is developed to analyze thermally agitated magnetization reversal in a single-domain ferromagnetic grain with a uniaxial anisotropy axis oriented at an arbitrary angle to a magnetic field. Random forces and phenomenological damping consistent with thermodynamics are introduced into the dynamic equations of the normal modes. This general approach reduces to the Landau-LifshitzGilbert formalism only when the magnetic energy is isotropic about the equilibrium position. A stochastic averaging method based upon a small damping parameter is used to transform the inherent two-dimensional problem into a one-dimensional form. The mean first exit time is calculated and the results for dynamic coercivity at different angles to the magnetic field are obtained. The method is ultilized to calculate the switching field versus pulse time for planar random media with noninteracting grains. The results fit well with direct Langevin simulation over short times and with Néel-Arrhenius models at long times. A general field and temperature dependent form of the attempt frequency, f[sub 0], is derived. [ABSTRACT FROM AUTHOR]

Presents a study which numerically investigated the magnetization process in ferromagnetic cubes. Cubic discretization procedure of the micromagnetic energy functional; Mathematical framework for describing the ferromagnetic particle; Computation of the complete hysteresis loops for a wide range of particle sizes.

Presents a study which examined the energy barriers for thermal reversal of interacting single domain ferromagnetic particles. Energy surfaces for various interaction strengths; Analytical solutions; Calculation of an effective volume.

We consider a single-domain ferromagnetic particle with uniaxial anisotropy coupled to a single-domain soft ferromagnetic particle (superparamagnetic particle). The problem of thermally agitated magnetization reversal in this case can be reduced to the random magnetization dynamics of the first particle with an effectively larger anisotropy field. The magnetic external field is also altered in a manner that depends on the sign of the coupling and can be either enhanced or suppressed. [ABSTRACT FROM AUTHOR]

The process of magnetization reversal in a fine ferromagnetic grain with a strong uniaxial anisotropy has been simulated for the case of an instantaneously applied reversal magnetic field. The “quasi” single-domain grain was considered as a system of 64 or 1000 subcubes coupled by exchange and dipole–dipole interactions. The system of Landau–Lifshitz equations was numerically solved without any phenomenological damping terms. The dynamic process is characterized by a rapid magnetization reversal accompanied by a decrease in the average magnetization. The system exhibits a nonlinear excitation of nonuniform magnetic oscillations (spin waves) driven by the uniform mode. We found limitations on magnetization reversal for small grain size and large applied field magnitude. The damping parameter has been obtained for small magnetization oscillations. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which modeled the magnetization domain structures in thin metallic films utilized as recording media using cellular automation on a two-dimensional triangular lattice. Computer simulation modeling of planar isotropic films; Results and discussion; Conclusions.

Presents information on a study which examines the thermally assisted reversal in noninteracting single domain particles through the use of a micromagnetic model with a stochastic fluctuation field. Presentation of the results of the thermal decay for a single domain particle; Introduction of a set of dimensionless variables; Conclusions.

Presents a study on the use of three-dimensional (3-D) micromagnetic model to examine nucleation field dependence on exchange length, particle size and external field angle for long ferromagnetic particles. Parameters used in the micromagnetic model; Conclusion.