  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.
