Superparamagnetic Transition and Local Disorder in CuFe2O4 Nanoparticles

TL;DR

This study investigates how ball-milling affects the structural and magnetic properties of CuFe2O4 nanoparticles, revealing superparamagnetic behavior, local disorder, and inhomogeneities at the nanoscale.

Contribution

It provides new insights into the effects of mechanical milling on nanoparticle size, magnetic transition, and local disorder in CuFe2O4.

Findings

Nanoparticle size decreases to ~7 nm after milling.

Superparamagnetic behavior observed at room temperature.

Local disorder and inhomogeneities increase with milling time.

Abstract

We present X-ray diffraction (XRD), M\"ossbauer spectroscopy (MS) and d.c. magnetization measurements performed on ball-milled CuFe2O4 samples. The average particle size <d> was found to decrease to the nanometer range after t=15 min of milling. Room temperature M\"ossbauer data showed that the fraction of particles above the blocking temperature TB increases with milling time, and almost complete superparamagnetic samples are obtained for <d> = 7(2) nm. Magnetization measurements below TB suggest spin canting in milled samples. The values of saturation moment mu_S reveal that site populations are slightly affected by milling. M\"ossbauer resonant intensities are accounted for on the basis of local disorder of Fe3+ environments, and the development of sample inhomogeneities of CuxFe3-xO4 composition.