Electron-spin resonance spectra of Ge-rich Bi-modified amorphous ${\left({\mathrm{Ge}}_{42}{\mathrm{S}}_{58}\right)}_{99.5-x}{\mathrm{Bi}}_x{\mathrm{Mn}}_{0.5}$ (as prepared and annealed) have been observed by use of ${\mathrm{Mn}}^{2+}$ as a microprobe for the first time. The data on the $g$ value and the line parameters in various samples studied show that the effects of addition of Bi to the Ge-rich composition ${\mathrm{Ge}}_{42}$${\mathrm{S}}_{58}$ and to the sulfur-rich composition ${\mathrm{Ge}}_{20}$${\mathrm{S}}_{80}$ are quite different, indicating a dissimilar microscopic environment. The behavior of the resonance line at $g\approx 2$ in the composition $x=2\mathrm{}$ is quite different from that in $x=0, 4$ samples. Results are discussed in the light of the Phillips cluster model and constraint theory [J. C. Phillips, Phys. Rev. B 36, 4265 (1987)].

• Received 3 October 1988

DOI:https://doi.org/10.1103/PhysRevB.39.11203