الفهرس 
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Abstract
polycrystalline bulk samples of yttrium iron garnet(y3fe5o-12) and mixed iron garnet(y3fe5- x alxo12) where x = 0. 5, 1. 5 and 2mol% , were prepared from high purity oxides according to the ceramic sintering procedure. the prepared samples were characterized by x- ray diffraction , infrared spectroscopy and mössbauer spectroscopy. all measurements were carried out at room temperature. the results of this study showed that : - the garnet phase of yttrium iron oxide (y3fe5o12) can be formed as the sintering temperature is 1400 °c and soaking time is 24 hours. the garnet phase could be obtained as a single phase, the lattice constant of the yttrium iron garnet(yig) unit cell was found as 12. 328 ao . the ir spectra of yig does not contain any bands of constituent compounds(y2o3, fe2o3 and al2o3), which indicates occurrence of complete solid- state reaction and transformation of these compounds into yig, in ir spectrum of yig two bands at 475 and 805 cm- 1 can be observed and are assigned to the stretching mode of yig tetrahedral. the mössbauer spectra of yttrium iron garnet (y3fe5o12), showed two sets of six lines. the lines were ascribed to the iron ions in the yttrium iron garnet phase. the iron ions were found to be located in two non- equivalent sites with different point symmetries: tetrahedral(d) and octahedral(a) sub lattice. the ratio between them is 1.5 , this indicate the presence of trivalent ferric ions only and yttrium iron garnet is ferromagnetic material. in substitutional solid solutions of mixed garnet y3alxfe5- xo12 where x = 0. 5, 1. 5 and 2mol%. for x = 0. 5mol%, the garnet phase of yttrium iron oxide (y3fe5o12) can be formed for x = 1. 5and 2mol%, the garnet phase of yttrium iron aluminum oxide (y3alfe4o12) can be formed. the lattice parameter decreased with the increasing of al content from x = 0. 5 to 2mol%. the ir spectrum of yalig showed some bands formed in yig at 475 and 805 cm- 1 but slightly( sharpening of the bands)and shifting , its bands towards high wave number , indicating that al ions are in d and a- site. the mössbauer spectra of mixed garnet yalig showed that iron ions are located in two non- equivalent sites with different point symmetries: tetrahedral(d) and octahedral(a) sub lattice. al substitution transforms the ferromagnetic yig material to paramagnetic material. there is no influence of milling time (6 and 72 hrs)on phase formation. only the lattice parameter increased in the early times of milling (< 6hrs) and arrived to approximately constant value in the milling time (6- 72 hrs). the ir spectra showed that increasing milling time to 6hrs resulted in increasing the band area of wave numbers (475 and 805 cm- 1). increasing milling time to 72hrs decreased the band area of the same previously mentioned wave numbers.