Magnetic viscosity and thermal activation energy
Abstract
Magnetic viscosity arises when the activation energy E required to produce a change in mangetization is provided thermally. Activation energy functions for single domain particles and materials with ``strong'' and ``weak'' domainwall pinning are discussed. The magnetic viscosity parameter S_{v}, given by kT(∂E/∂H)^{1}_{T}, where kT is the Boltzmann energy and H is the magnetic field, is shown to be proportional to kT/(v M_{s}), where M_{s} is the spontaneous magnetization and v is the activation volume swept out as the energy barrier is overcome. For single domain particles and strong domainwall pinning the constant of proportionality is one while for weak pinning it is 1/2. The generality of this simple relationship is shown to be independent of the details of the activation model.
 Publication:

Journal of Applied Physics
 Pub Date:
 June 1986
 DOI:
 10.1063/1.336671
 Bibcode:
 1986JAP....59.4129G