Polydispersity-linked Memory Effects in a Magnetic Nanoparticle System

TL;DR

This study investigates how polydispersity influences memory effects in magnetic nanoparticle systems, revealing that dipolar interactions suppress memory and that a flat size distribution optimizes memory retention.

Contribution

It demonstrates the impact of size distribution and interactions on magnetic memory effects, providing insights into nanoparticle behavior at low temperatures.

Findings

Memory effects are observed in dc magnetization measurements.

Dipolar interactions suppress the memory effect.

A flat size distribution enhances memory retention.

Abstract

We have performed a series of measurements on the low temperature behavior of a magnetic nano-particle system. Our results show striking memory effects in the dc magnetization. Dipolar interactions among the nano-particles {\em suppress} the memory effect. We explain this phenomenon by the superposition of different super paramagnetic relaxation times of single domain magnetic nano- particles. Moreover, we observe a crossover in the temperature dependence of coercivity. We show that a dilute dispersion of particles with a flat size distribution yields the best memory.