Fluctuations in the Local Fields Due to Al3+ Ions Substitution in the M-Type Barium Hexaferrites, BaFe12-xAlxO12

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Abstract
The effects of aluminum substitution into the M-type Ba-hexaferrites on the saturation magnetization and Mossbauer spectrum of these ferrites are studied. The saturation magnetization M s of the BaFe 12-x Al x O 12 is seen to decrease linearly with increasing Al substitution. The Mossbauer spectrums for the x = 0.1, 0.2 and 0.6 specimens were all resolved as superpositions of four sub-spectrums (12k, 4 fiv +2 a , 4 fvi and 4e). The half width of the Mossbauer lines of the 4 fiv+2a sextets is seen to broadening as Al ions are substituted into the ferrite. No broadening is seen in the lines of the other sextets. These behaviors (the line broadening and the linear decrease in M s ) are consistent with the Al 3+ ions substituting preferentially into the 2a sites.