# Magnetization Dynamics in 1D Chains of Ferromagnetic Nanoparticles Coupled with Dipolar Interactions: Blocking Temperature

## TL;DR

This paper investigates how dipolar interactions and external magnetic fields influence the blocking temperature in one-dimensional chains of ferromagnetic nanoparticles, highlighting the importance of geometry and field orientation.

## Contribution

It provides a qualitative analysis of how the blocking temperature varies with interparticle distance and external field orientation in different chain geometries.

## Key findings

- Blocking temperature depends on interparticle distance and field orientation.
- Geometry and external magnetic field significantly influence relaxation dynamics.
- Dipolar interactions can either increase or decrease the blocking temperature depending on conditions.

## Abstract

There is so far no clear-cut experimental analysis that can determine whether dipole-dipole interactions enhance or reduce the blocking temperature $T_{B}$ of nanoparticle assemblies. It seems that the samples play a central role in the problem and therefore, their geometry should most likely be the key factor in this issue. Yet, in a previous work, J\"onsson and Garcia-Palacios did investigate theoretically this problem in a weak-interaction limit and without the presence of an external DC field. Based on symmetry arguments they reached the conclusion that the variation of the relaxation rate is monotonous. In the presence of an external magnetic field we show that these arguments may no longer hold depending on the experimental geometry. Therefore, the aim of this paper is to evaluate the variation of $T_{B}$ for a model system consisting of a chain of ferromagnetic nanoparticles coupled with long-range dipolar interaction with two different geometries. Rather than addressing a quantitative analysis, we focus on the qualitative variation of $T_{B}$ as a function of the interparticle distance a and of the external field $h$. The two following situations are investigated: a linear chain with a longitudinal axial anisotropy in a longitudinal DC field and a linear chain with a longitudinal axial anisotropy in a transverse field.