Tuning the Surface States of $Fe_3O_4$ Nanoparticles for Enhanced Magnetic Anisotropy and Induction Efficacy

TL;DR

This study demonstrates that surface modification of $Fe_3O_4$ nanoparticles enhances their magnetic anisotropy and induction efficacy, significantly improving their performance in biomedical applications like hyperthermia and MRI.

Contribution

It introduces a surface-state engineering method to optimize $Fe_3O_4$ nanoparticles for improved magnetic properties and biomedical efficacy.

Findings

Surface treatment forms a ${ extgamma}$-$Fe_2O_3$ shell confirmed by multiple spectroscopy techniques.

Enhanced magnetic anisotropy increases specific absorption rate by 140%.

Surface modification suppresses spin-glass transition and raises blocking temperature.

Abstract

Magnetite ($Fe_3O_4$) nanoparticles are crucial for biomedical applications, including magnetic hyperthermia, targeted drug delivery, and MRI contrast enhancement, due to their biocompatibility and unique physicochemical properties. Here, we investigate how surface states influence their induction performance. Heat treatment removes surface water and FeOOH, forming a ${\gamma}$-$Fe_2O_3$ shell, as confirmed by synchrotron powder diffraction, neutron powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and time-of-flight inelastic neutron spectroscopy. AC magnetic susceptibility measurements reveal that this surface modification enhances magnetic anisotropy and reduces the spin relaxation time, leading to a 140% increase in the specific absorption rate. Additionally, the increased anisotropy suppresses the low-temperature clustered spin-glass transition and raises the blocking temperature. These findings highlight surface-state engineering as a powerful approach to optimizing $Fe_3O_4$ nanoparticles for biomedical applications.