$^{57}$ Fe Emission Mössbauer Study on $Gd_3 Ga_5 O_{12}$ implanted with dilute $^{57} Mn$

$^57$Fe emission Mössbauer spectroscopy has been applied to study the lattice location and properties of Fe in gadolinium gallium garnet $Gd_3 Ga_5 O_{12}$ (GGG) single crystals in the temperature interval 300 – 563 K within the extremely dilute (<10$^{−4}$ at.%) regime following the implantation of$^{57}$Mn (T$_{1 / 2}$= 1.5 min.) at ISOLDE/CERN. These results are compared with earlier Mössbauer spectroscopy study of Fe-doped gadolinium gallium garnet $Gd_3 Ga_5 O_{12}$(GGG), with implantation fluences between 8×10$^{15}$ and 6×10$^{16}$ atoms cm $^{−2}$. Three Fe components are observed in the emission Mössbauer spectra: (i) high spin Fe$^{2+}$ located at damage sites due to the implantation process, (ii) high spin Fe$^{3+}$ at substitutional tetrahedral Ga sites, and (iii) interstitial Fe, probably due to the recoil imparted on the daughter $^{57∗}$Fe nucleus in the $\beta^−$ decay of $^{57}$Mn. In contrast to high fluence $^{57}$Fe implantation studies the Fe3+ ions are found to prefer the tetrahedral Ga site over the octahedral Ga site. No annealing stages are evident in the temperature range investigated. Despite the very low concentration, high-spin Fe$^{3+}$ shows fast spin relaxation, presumably due to an indirect interaction between nearby gadolinium atoms.