Correlation between tunneling magnetoresistance and magnetization in dipolar coupled nanoparticle arrays

TL;DR

This study investigates how dipolar interactions influence tunneling magnetoresistance (TMR) and magnetization in nanoparticle arrays, revealing complex dependencies on field direction and interaction strength through simulations.

Contribution

It introduces a combined resistor network and micromagnetic simulation approach to analyze the impact of dipolar coupling on TMR and magnetization in nanoparticle arrays, highlighting new interaction effects.

Findings

Dipolar interactions suppress maximum TMR effect.

Maximum TMR depends on field direction and interaction strength.

Behavior differs between soft and hard magnetic systems.

Abstract

The tunneling magnetoresistance (TMR) of a hexagonal array of dipolar coupled anisotropic magnetic nanoparticles is studied using a resistor network model and a realistic micromagnetic configuration obtained by Monte Carlo simulations. Analysis of the field-dependent TMR and the corresponding magnetization curve shows that dipolar interactions suppress the maximum TMR effect, increase or decrease the field-sensitivity depending on the direction of applied field and introduce strong dependence of the TMR on the direction of the applied magnetic field. For off-plane magnetic fields, maximum values in the TMR signal are associated with the critical field for irreversible rotation of the magnetization. This behavior is more pronounced in strongly interacting systems (magnetically soft), while for weakly interacting systems (magnetically hard) the maximum of TMR (Hmax) occurs below the coercive field (Hc), in contrast to the situation for non-interacting nanoparticles or in-plane fields (Hmax=Hc). The relation of our simulations to recent TMR measurements in self-assembled Co nanoparticle arrays is discussed.