Structural and Mossbauer studies of ball milled Co-Zn Y-type hexaferrites

TL;DR

This study investigates how ball milling affects the structure, microstructure, and magnetic hyperfine interactions in Co-Zn Y-type hexaferrites using various characterization techniques.

Contribution

It provides detailed insights into the structural stability, particle size reduction, and hyperfine parameter changes due to ball milling in Co-Zn hexaferrites.

Findings

Single phase Y-type hexaferrite persists after milling

Particle size reduces by a factor of 10 after four hours of milling

Hyperfine fields decrease exponentially with milling time

Abstract

Y-type hexaferrite samples Ba2ZnxCo2-xFe12O22 with x = 0, 1 and 2 were prepared from precursors synthesized by the citrate sol-gel auto combustion method. The powders were sintered at 1100{\deg} C for four hours. X-ray diffraction, scanning electron microscopy and M\"ossbauer spectroscopy were used to investigate the effect of ball milling on the structure, microstructure and on the hyperfine parameters. X-ray diffraction revealed the presence of a single Y-type hexaferrite in all sintered samples. This phase persisted in samples milled for periods up to four hours. Scanning electron microscopy images indicated that the particles changed shape, and their sizes reduced by a factor of 10 for milling times of four hours. Room temperature M\"ossbauer spectra of the hexaferrites elucidated the distribution of the various cations at the various sites of the hexaferrite lattice. The hyperfine field (Bhf) associated with each component was found to decrease almost exponentially with increasing milling time. The reduction in hyperfine field was associated with the weakening of the superexchange interactions between the spin-up and spin-down sublattices as a consequence of replacing Co2+ magnetic ions by non-magnetic Zn2+ ions and with the microstructure in the milled samples.