Investigation of the substitutional Fe2+ center in Y3Al5O12 by acoustic EPR

Room Temperature Ferromagnetism in Dilute Iron-Doped Yttrium Aluminum Garnet Polycrystals

“…However, it was shown that the only possible source of electronic conduction is excess electrons originated from oxygen vacancy in Y 3 Al 5− x Fe x O 12 garnets. As these electrons favor occupying an empty iron 3d orbital, ,– they should increase the isomer shift values noticeably. In the bound polaron model, which was derived for the DMI materials and also outlined for the case of the present samples in the previous paragraph, the locally trapped electrons do not affect much the electronic state of iron ions as seen by Mössbauer spectroscopy.…”

“…In addition to mixing aluminum and iron in the (a) and (d) sites, oxygen nonstoichiometry and even cation impurities were reported to play significant role in the transport properties of garnets . Besides enhancing ionic conductivity, oxygen vacancies were found to favor reduction of Fe 3+ ions into Fe 2+ , where the extra electrons can contribute to the itinerant charge carriers. ,– Moreover, divalent cation impurities were expected to provoke competition between formation of oxygen vacancies and oxidation of iron ions into Fe 4+ . However, Mössbauer spectra of Y 3 Al 5− x Fe x O 12 garnets presented only trivalent iron ions on both crystallographic sites. – ,, …”

“…22 Besides enhancing ionic conductivity, oxygen vacancies were found to favor reduction of Fe 3+ ions into Fe 2+ , where the extra electrons can contribute to the itinerant charge carriers. 21,[29][30][31] Moreover, divalent cation impurities were expected to provoke competition between formation of oxygen vacancies and oxidation of iron ions into Fe 4+ . 22 However, Mo ¨ssbauer spectra of Y 3 Al 5-x Fe x O 12 garnets presented only trivalent iron ions on both crystallographic sites.…”