57Fe Emission Mossbauer study on Gd3Ga5O12 implanted with dilute 57Mn

Abstract

57Fe emission M¨ossbauer spectroscopy has been applied to study the lattice location and properties of Fe in gadolinium gallium garnet Gd3Ga5O12 (GGG) single crystals in the temperature interval 300 – 563 K within the extremely dilute (<10−4 at.%) regime following the implantation of 57Mn (T1/2 = 1.5 min.) at ISOLDE/CERN. These results are compared with earlier M¨ossbauer spectroscopy study of Fe-doped gadolinium gallium garnet Gd3Ga5O12(GGG), with implantation fluences between 8×1015 and 6×1016 atoms cm−2. Three Fe components are observed in the emission M¨ossbauer spectra: (i) high spin Fe2+ located at damage sites due to the implantation process, (ii) high spin Fe3+ at substitu-tional tetrahedral Ga sites, and (iii) interstitial Fe, probably due to the recoil imparted on the daughter 57∗Fe nucleus in the β− decay of 57Mn. In contrast to high fluence 57Fe implanta-tion 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 Fe3+ shows fast spin relaxation, presumably due to an indirect interaction between nearby gadolinium atoms.