Hyperfine Interact (2010) 198:295–302 DOI 10.1007/s10751-010-0234-z Mössbauer studies of Y 3 Fe 5−x Al x O 12 nanopowders prepared by mechanochemical method Z. Azadi Motlagh · M. Mozaffari · J. Amighian · A. F. Lehlooh · M. Awawdeh · S. Mahmood Published online: 1 December 2010 © Springer Science+Business Media B.V. 2010 Abstract A series of Al substituted yttrium iron garnet (Al-YIG) nanopowders with nominal formula of Y 3 Fe 5−x Al x O 12 which x varied in steps of 0.0, 0.5, 1.0, 1.5 and 2.0 were prepared via mechanochemical processing. The samples were milled for 40 h in a high energy planetary mill and then calcined at different temperatures from 1,300 to 1,100 ◦ C. X-ray diffraction patterns reveal that the structure of nanopow- ders are bcc and the garnet phase has been obtained after calcining. The average crystallite sizes are in the range of 24–45 nm, using Scherrer’s formula. The lattice constant of the samples decreases by increasing Al concentration. To investigate the site preference of Al 3+ ions, room temperature 57 Fe Mössbauer spectra for the samples were recorded and analyzed. The hyperfine field values for octahedral and tetrahedral sites of the samples decrease by increasing x value. This decrease in magnetic hyperfine field reflects a reduction of the superexchange interaction by the progressive substitution of Al for Fe, which is also evident in the behavior of the magnetization and T C for the samples. Z. Azadi Motlagh (B ) · J. Amighian Faculty of Science, Department of Physics, Isfahan University, Isfahan, Iran e-mail: zdmtlgh@yahoo.com M. Mozaffari Faculty of Science, Department of Physics, Razi University, Taghbostan, Kermanshah, Iran J. Amighian Faculty of Science, Department of Physics, Islamic Azad University, Najafabad Branch, Najafabad, Iran A. F. Lehlooh · M. Awawdeh · S. Mahmood Department of Physics, Yarmouk University, Irbid 211-63, Jordan