Trapdoor Viscous Remanent Magnetization

Abstract

Abstract Viscous remanent magnetization (VRM) in multidomain (MD) particles has many puzzling properties that deviate from the current VRM theory, based on Néel's single‐domain model of magnetic particles with an almost symmetric double‐well potential. In larger magnetic particles experimental evidence indicates that more complex magnetization structures preferentially change from high‐energy states to low‐energy states with large energy differences, such that VRM is preferentially acquired by directed magnetization changes in strongly asymmetric double‐well potentials. Here, a statistical model based on this ’trapdoor’ VRM (tdVRM) naturally explains the experimental observations of initial‐state dependence, time‐lag variation, non‐linear logt dependence, and acquisition‐decay asymmetry for MD VRM. It is discussed how tdVRM can be experimentally distinguished from single‐domain VRM and how the new theory can help to improve age determination by VRM analysis.

Keywords

• viscous magnetization
• multidomain magnetite