The Stoner-Wohlfarth model of ferromagnetism

Abstract

The physics of magnetic state change in single domain magnetic grains (called Stoner particles) is interesting from the fundamental as well as the applied points of view. A change in magnetization can be finely tuned with a specific time variation of an externally applied magnetic field. It may also occur naturally (without application of a field) at very low temperature with quantum tunneling and at higher temperature with thermal excitation. The optimal (usually shortest) time altering the magnetisation along with the smallest applied magnetic field are sought in technological applications such as high-density reading or writing of information, spintronics, quantum information and quantum communication systems. This work reviews the magnetization change with a time dependent field and temperature and discusses the time it takes to alter the magnetization as a function of the control parameter chosen, temperature and material parameters.

“Magnetic Force Microscopy and Energy Loss Imaging of Superparamagnetic Iron Oxide Nanoparticles”

“…The instantaneous magnetic moment of each SP NP is continuously undergoing stochastic inversion between opposite directions. The Nèel-Brown model18 for uniaxial spherical particles describes this physical process by a spin relaxation time, representing the average time for a NP magnetic moment to flip along the easy magnetization axis. This process is thermally activated, with exponential dependence on the particle magnetization and thus on its volume, as described by the Arrhenius law1.…”

“…As a result, small changes in NP size can lead to very different magnetic properties at RT. The SP state is of interest since the non-magnetic particles can still be magnetized by an external field, which will favor one of the two opposite easy magnetization directions, leading to a stable magnetic configuration as described by the Stoner-Wohlfarth model1819. In this way, field controlled SP NP assemblies can be induced in a colloidal dispersion132021.…”

The Effect of Cyclic Movement of Magnets on the Sedimentation of Magnetic Nanoparticles in Magnetofection Devices: Computer Simulation

“…As mentioned above, we will consider only two forces here -the magnetic force and the viscous drag force. MNP are onedomain magnetic nanoparticles [7] with a large constant magnetic moment: µ…”

Impact of Resistive-Bridge Defects in TAS-MRAM Architectures

“…The first MRAM generation (FIMS) rel Wohlfarth theory of coherent rotation i particles [9]. In this approach, the energy r the magnetization is minimized by applyin two perpendicular magnetic fields.…”