Dynamical study of remanent magnetization in nanoparticles

For collections of noninteracting nanoparticles, we study the reduced static remanent magnetization, mR, produced by the removal of a saturating magnetic field. We show that, except for special cases such as easy uniaxial anisotropy, mR depends on both the ramp-down rate of the field and the energy dissipation rate of the spin dynamics. Using the Landau-Lifshitz equation, we illustrate this result with explicit dynamical calculations of mR for cubic and for mixed cubic-uniaxial anisotropies. © 2001 Elsevier Science B.V. All rights reserved.