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

摘要

The present study is concerned with the fabrication and characterization ofMe2Y substituted hexaferrites, Ba2Me2Fe12-xTxO22 (Me = Co2+, Mg2+, and Cr2+,and T = Fe3+, and Ga3+). The samples were prepared by the conventional ballmilling technique and sintering at 1200{\deg} C. The effect of the choices ofMe and T ions on the structural and magnetic properties of the hexaferriteswere investigated. XRD patterns, magnetic parameters, and M\"ossbauer spectraof 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, andM-type and BaCrO4 minority phases were observed in the XRD pattern of thesample. The small increase in saturation magnetization from about 34 emu/g upto 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 ofthe M-type phase in this sample. The high coercivity (1445 Oe) of this sampleis evidence of the transformation of the material from a typically softmagnetic material (Y-type) to a hard magnet (M-type). The Ga-substitution forFe in Co2Y did not affect the saturation magnetization significantly, but thecoercivity was reduced. However, the sample Ba2CoMgFe11GaO22 exhibited asignificant reduction of the saturation magnetization down to a value 26.6emu/g, which could be due to the attenuation of the super-exchange interactionsinduced by the Mg2+ substitution.