Memory in nanomagnetic systems: Superparamagnetism versus Spinglass behavior

TL;DR

This paper compares superparamagnetic and spin glass models to explain memory effects in nanomagnetic systems, highlighting the roles of particle relaxation and interactions.

Contribution

It clarifies the conditions under which superparamagnetism or spin glass behavior explains aging phenomena in nanomagnets.

Findings

Superparamagnetic relaxation explains many aging effects.

Interactions and randomness lead to distinctive signatures.

Size distribution of particles is crucial for modeling.

Abstract

The slow dynamics and concomitant memory (aging) effects seen in nanomagnetic systems are analyzed on the basis of two separate paradigms : superparamagnets and spinglasses. It is argued that in a large class of aging phenomena it suffices to invoke superparamagnetic relaxation of individual single domain particles but with a distribution of their sizes. Cases in which interactions and randomness are important in view of distinctive experimental signatures, are also discussed.