# Structural, Magnetic, and Electron Spin Resonance Properties of Nickel Nanoferrites Synthesized by High‐Energy Ball Milling

## TL;DR

This paper studies how high-energy ball milling affects the structure and magnetic properties of nickel nanoferrites, which could be useful in biomedical applications.

## Contribution

The study demonstrates that high-energy ball milling improves crystallinity and magnetic properties of NiFe2O4 nanoparticles for biomedical use.

## Key findings

- X-ray diffraction showed transformation to a single-phase cubic spinel NiFe2O4 structure with milling time.
- Milling time increased g-values and improved soft ferromagnetic behavior, suitable for high-frequency devices.
- ESR results indicated reduced resonance fields and decreased spin-spin relaxation time with longer milling.

## Abstract

Nanocrystalline NiFe2O4 was synthesized using high‐energy ball milling. The effect of milling time on structural and magnetic properties was investigated. X‐ray diffraction results revealed a progressive transformation from mixed NiO–Fe2O3 precursor phases to a single‐phase cubic spinel NiFe2O4 structure with crystallite sizes ranging from 33.64 to 41.17 nm. The scanning electron microscopy showed small grains attaching to big grains for 1 h milled sample. The big grains disappear with increasing milling time. Homogeneous nanoparticles, spherically shaped and agglomerated nanoparticles, were observed for samples that were milled for 5, 10, and 15 h. Energy‐dispersive X‐ray spectroscopy confirmed the presence of all expected elements. The nature of M
–
H loops for all the samples shows soft ferromagnetic behavior. The Electron spin resonace (ESR) results revealed the reduction of resonance field with increasing milling time. The g‐values increased with milling time. The obtained high g‐values make NiFe2O4 oxides suitable for applications in high‐frequency devices. The spin–spin (τ
1) relaxation time decreased with increasing milling, time while the spin–lattice (τ
2) showed improvement.

One of the properties of nickel ferrite materials that is drawing attention is their potential for biomedical applications. In this work, NiFe2O4 nanoparticles from NiO and Fe2O3 were produced using high‐energy ball milling. Milling time enhanced crystallinity. Magnetization tests and ESR studies revealed soft ferromagnetic materials, emphasizing their importance in biomedical applications.© 2026 WILEY‐VCH GmbH