Electron paramagnetic resonance study of Mn²⁺ and Cu²⁺ spin probes in (Ag₂S) _x(GeS₂)_1-x glasses

Mn²⁺ and Cu²⁺ spin probes have been introduced in glassy (Ag₂S)_x(GeS₂)_1-x (0 ≤ x ≤ 0.8). The electron paramagnetic resonance spectra related to Mn²⁺ show a poorly resolved hyperfine structure at g = 2 and a characteristic line at g = 4.3 ascribed to the presence of Mn²⁺ in the center of GeS₄ tetrahedra. For small contents of Mn²⁺, hyperfine structure is resolved as x increases to the limit x = 0.55 and not resolved when x ≥ 0.6. The Cu²⁺ probe leads to a well resolved signal when x = 0.4. No signal is observed for x < 0.3. These results seem to confirm the presence of a phase separation domain for x < 0.3 and the changes of the local structure of the probes with the appearance of micro-crystallinity due to the Ag₈GeS₆ phase when x ≥ 0.55.