Rare‐Earth Ion Local Environments in Nd:Al₂O₃‐P₂O₅‐K₂O Glass Studied by Electron Paramagnetic Resonance Spectroscopies

The rare‐earth local environments of Nd:Al 2 O 3 ‐P 2 O 5 ‐K 2 O glass with different P/Al ratios are analyzed using electron paramagnetic resonance (EPR). The echo‐detected field sweep (EDFS) line‐shape change hints at a modification of the local environment around Nd 3+ ion by various P/Al ratios. The coordination sphere structure of Nd 3+ ion is determined by three and four pulse electron spin echo envelope modulation (ESEEM) spectra. The off‐diagonal signal corresponding to 31 P Larmor frequency confirms that the second‐order coordination sphere of Nd 3+ ion is almost occupied by P atoms. Al is located at the higher‐order Nd 3+ coordination sphere as only diagonal resonance corresponding to the 27 Al was detected, the content of which rapidly increases with decreasing P/Al ratio.