Môssbauer, optical and epr spectral studies of alunite

Môssbauer, optical and EPR spectral studies are made on alunite minerai. The Môssbauer spectrum of alunite exhibit the characteristic pattern of Zeeman hyperfine splitting of iron. It shows the magnetic ordering of the sample and the calculated internai field is 523 kG. The isomer shift and quadrupole splitting are δ = 0.3757 and QS = 0.155 mm s-1indicating the presence of iron in the Fe3+State with antiferromagnetic nature. The optical absorption studies suggest octahedral symmetry for Fe3 +in the sample. Three strong and sharp Unes in the EPR spectrum with g values 7.984, 5.791 and 3.962 suggest a large anisotropy for Fe3+in the sample. The EPR spectrum also reveal the presence of vanadium and manganèse as trace impurities in the sample. © 1992 IOP Publishing Ltd.