The garnet ferrites have the general formula RFe5O12, where R is one of the rare earth metal ions (Y, Gd, Dy, Sm, Eu, Ho, Er, Tm, Tb and Lu). The first trail for synthesis of garnet Yttrium ferrite (Y3Fe5O12) was done by Bertaut and Forret in 1956 [39], this trial was followed by another one in 1957 when Geller and Gilleo prepared and investigated Gd3Fe5O12 [40]. The garnet ferrites have complex crystal structure with cubic shape. The cubic unit cell of garnet ferrites R3Fe5O12 contains 8 formula units or 160 atoms with O2 as widespread ions (96 ions). The trivalent rare earth ions (Y, Gd, Dy) consider a typical example for garnet ferrites (R3Fe5O12). The remaining 64 sites of cations is considerably more complex where; 24 dodecahedral sites were occupied by Y3+, 24 tetrahedral sites were occupied by Fe3+ while 16 octahedral sites were occupied by Fe3+ (fig.7). The cations in octahedral and dodecahedral sites can substitute by transition metal cations.
