2021/10/08 by C. A. M. Iglesias, Iglesias, C. A., J. C. R. de Araújo +23
Earth and Planetary Sciences · Chemistry · Materials Science · #nanoparticles nucleation surface interactions #Electrostatics and Colloid Interactions #Gold and Silver Nanoparticles Synthesis and Applications
paper · pdf · doi:10.48550/arxiv.2110.04139
We report a simple, efficient manner to assess magnetic interactions, more specifically the exchange interaction, in systems as blocked magnetic nanoparticles. Specifically, we investigate what is the theoretical limit for the external magnetic susceptibility in a system described by the plain old Stoner-Wohlfarth model. We go beyond and introduce a general mean field theory for interacting systems, thus estimating how the magnetic susceptibility is affected due to the dipolar and exchange interactions inside the system. We disclose a fundamental inequality for the magnetic susceptibility and show its violation is an unambiguous signature of the existence of exchange interactions between nanoparticles in a collective system. To test the robustness of our theoretical achievements, we examine magnetization measurements and Henkel plots for blocked magnetic nanopowders. The agreement between experiment and theory provides evidence to confirm the validity of our findings.