Magnetically Superior and Easy to Handle L10-FePt Nanocrystals

TL;DR

This paper presents a novel synthesis method for monodisperse L10-FePt nanocrystals with high coercivity, easy dispersibility in water, and maintained magnetic properties through a protective SiO2 coating and specific thermal treatment.

Contribution

It introduces a new synthesis approach enabling high-temperature formation of L10-FePt nanocrystals with enhanced magnetic properties and facile water dispersibility, overcoming previous handling challenges.

Findings

High coercivity of 18.5 kOe at room temperature.

Successful recovery of nanocrystals in water dispersion.

Retention of magnetic orientation in dispersed nanocrystals.

Abstract

We report a successful synthesis of monodisperse L10-FePt nanocrystals which are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2-coating, the thermal treatment needed to form the L10 structure can be done even at 900 oC without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L10-FePt nanocrystals in a water-dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5 kOe at room temperature in spite of their core size of only 6.5 nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained.