High-spin europium and gadolinium centers in yttrium–aluminum garnet

High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopic Analysis of Metal–Ligand Covalency in a 4f7 Valence Series (Eu2+, Gd3+, and Tb4+)

“…Although scarce, some solid-state materials containing Tb 4+ have been investigated through EPR and yielded a diverse range of g values. ,− In these cases, the g values in different host lattices span 1.997(5)–2.0146(4). The highest values were obtained in ThO 2 and ThSiO 4 host lattices, where g = 2.0146(4) and 2.011(5), respectively. , Similarly, g values for Eu 2+ and closely related Gd 3+ complexes exhibit a reduced g value compared to g e . ,,, A qualitative comparison between the values among materials containing Eu 2+ , Gd 3+ , or Tb 4+ is available only in pairs (e.g., Eu 2+ /Gd 3+ or Gd 3+ /Tb 4+ in related hosts/sites). The lack of close structural similarity, combined with a dependence on the local structure, makes it difficult to definitively determine the effect of the metal identity and highlights the importance of the close structural congeners in this work.…”

“…In cases where S ≥ 2, the spin system may need to be characterized by fourth-order ZFS terms, and even sixth-order terms for S ≥ 3. , In this work, we have limited the analysis to only second-order terms as not to overparametrize the results. In extended lattice systems containing 4f 7 ions as dopants in high-symmetry sites, e.g., the Y 3+ site in yttrium aluminum garnet (Y 3 Al 5 O 12 ) and the Pb 2+ site in PbWO 4 (both materials have been used as hosts for Eu 2+ and Gd 3+ ) − or thoria (host for Tb 4+ ), it is possible to extract fourth- and sixth-order ZFS terms, although these are much smaller than the D (=3 B 2 0 ) term. To simplify the analysis, a new parameter, Δ 8 S, defined as the energetic separation between the highest and lowest m S states of the S = 7 / 2 ground state, is employed (vide infra).…”

“…71,77 Similarly, g values for Eu 2+ and closely related Gd 3+ complexes exhibit a reduced g value compared to g e . 67,68,70,78 A qualitative comparison between the values among materials containing Eu 2+ , Gd 3+ , or Tb 4+ is available only in pairs (e.g., Eu 2+ /Gd 3+ or Gd 3+ /Tb 4+ in related hosts/sites). The lack of close structural similarity, combined with a dependence on the local structure, makes it difficult to definitively determine the effect of the metal identity and highlights the importance of the close structural congeners in this work.…”

The Gd–Ce Cross-Relaxation Effects in ODMR via Ce3+ Emission in Garnet Crystals

“…in YAG has been studied in [23,24], but the obtained parameters were significantly different. According to [25], the spin Hamiltonian parameters of For low concentrations of isolated Gd 3? ions in non-magnetic crystals (e.g., garnet host crystals), EPR spectrum consists of seven fine-structure lines for each of the six magnetically non-equivalent centres.…”