Modification of the Magnetic Properties of Co2Y Hexaferrites by Divalent and Trivalent Metal Substitutions

TL;DR

This study investigates how divalent and trivalent metal substitutions affect the structural and magnetic properties of Co2Y hexaferrites, revealing phase transformations and changes in magnetic behavior through experimental characterization.

Contribution

It provides new insights into the effects of specific metal substitutions on the phases and magnetic properties of Co2Y hexaferrites, including phase transformation from Y-type to M-type and magnetic property modifications.

Findings

Small increase in saturation magnetization with CoCr substitution.

Transformation from soft to hard magnetic phase with Cr2+ substitution.

Significant reduction in saturation magnetization with Mg2+ substitution.

Abstract

The present study is concerned with the fabrication and characterization of Me2Y substituted hexaferrites, Ba2Me2Fe12-xTxO22 (Me = Co2+, Mg2+, and Cr2+, and T = Fe3+, and Ga3+). The samples were prepared by the conventional ball milling technique and sintering at 1200{\deg} C. The effect of the choices of Me and T ions on the structural and magnetic properties of the hexaferrites were investigated. XRD patterns, magnetic parameters, and M\"ossbauer spectra of the Co2Y were consistent with a single phase Y-type hexaferrite. However, the CoCr-Y sample was found to be dominated by the Y-type hexaferrite, and M-type and BaCrO4 minority phases were observed in the XRD pattern of the sample. The small increase in saturation magnetization from about 34 emu/g up to 37.5 emu/g was therefore attributed to the development of the M-type phase. On the other hand, XRD pattern of the Cr2Y sample indicated the dominance of the M-type phase in this sample. The high coercivity (1445 Oe) of this sample is evidence of the transformation of the material from a typically soft magnetic material (Y-type) to a hard magnet (M-type). The Ga-substitution for Fe in Co2Y did not affect the saturation magnetization significantly, but the coercivity was reduced. However, the sample Ba2CoMgFe11GaO22 exhibited a significant reduction of the saturation magnetization down to a value 26.6 emu/g, which could be due to the attenuation of the super-exchange interactions induced by the Mg2+ substitution.