Dynamical study of remanent magnetization in nanoparticles

Abstract For collections of noninteracting nanoparticles, we study the reduced static remanent magnetization, m R , produced by the removal of a saturating magnetic field. We show that, except for special cases such as easy uniaxial anisotropy, m R 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 m R for cubic and for mixed cubic–uniaxial anisotropies.