We calculate the electron spin resonance (ESR) spectra associated with the spin carrying nonlinear excitations such as neutral solitons, triplet excitons as well as electron and hole polarons for halogen-bridged mixed-valence transition metal (MX: M = Pt, X = Cl,Br,I) linear chain materials within a discrete, 3/4-filled, two-band, tight-binding extended Peierls-Hubbard model 1. The strongly distorted and localized CDW material, PtCl, is contrasted with the weak CDW, delocalized material, PtBr. The hyperfine structure in the ESR spectra arises from the spin density on the Pt atoms while the superhyperfine structure is attributed to a small spin density present on the halogen sublattice. These theoretical predictions are compared with the recent experimental ESR data on photoinduced defects in PtX materials.
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