Energy product of cylindrical FePt@CoFe2 and FePt@Fe nanoparticles

R M Souza,M S Nunes,Ana L Dantas,Y S M Santos,L L Oliveira,A S Carriço

doi:10.1063/1.5129535

Abstract

We report a theoretical discussion of the impact the composition on the maximum energy product ((BH)max) of core@shell FePt@CoFe2 and FePt@Fe nanocylinders. We have found that the best composition is determined by the competing trends imposed by a strong ferromagnetic core@shell interface exchange energy, and the core@shell dipolar interaction energy. The dipolar interaction has a negative impact on the nanocylinder (BH)max value, for shell thickness above a shell material dependent threshold value. We have also found that Fe is the best shell material owing to its much larger exchange stiffness.

Highlights

Systems composed of spherical bimagnetic core-shell nanoparticles have been considered for several applications of current interest.1 Combining different functionalities of two magnetic materials, into the effective magnetic properties of a single nanoparticle, one may optimize systems for key applications such as permanent magnets, recording media, and magnetic hyperthermia.1nanomagnets are currently being considered for designing arrays to produce artificial spin-orbit systems using onedimensional quantum wires.2–5 These applications require small size magnets with controllable stray field strengths
Recent reports on circular and rectangular cylindrical core@shell nanoparticles6,7 reveal that new magnetic phases emerge from the dipolar interaction coupling core and shell magnetic moments
We presently report a theoretical discussion of the impact coreshell composition on the maximum energy product of FePt@CoFe2 and FePt@Fe nanocylinders, with the magnetization along the cylindrical axis

Summary

INTRODUCTION

Systems composed of spherical bimagnetic core-shell nanoparticles have been considered for several applications of current interest. Combining different functionalities of two magnetic materials, into the effective magnetic properties of a single nanoparticle, one may optimize systems for key applications such as permanent magnets, recording media, and magnetic hyperthermia.. Nanomagnets are currently being considered for designing arrays to produce artificial spin-orbit systems using onedimensional quantum wires.2–5 These applications require small size magnets with controllable stray field strengths. The small value of the exchange stiffness favors the formation of twisted states in the CoFe2 shell, reducing the core@shell magnetization. It favors switching at low external field values in the demagnetization quadrant and dropping the maximum energy product value.

THEORETICAL MODEL

RESULTS AND DISCUSSIONS

CONCLUSIONS