Electron-paramagnetic-resonance study of the Cr³⁺ and Ni ²⁺ ions and the (SCl)^2- defect in FeS₂

An electron-paramagnetic-resonance study of the iron pyrite crystals grown by the method of chemical-vapor transport is reported. Cr³⁺ and Ni²⁺ ions were detected as substitutional impurities. An effective spin S =1/2 defect species that exhibits hyperfine couplings to the two natural isotopes of chlorine was detected in sulfur-deficient FeS₂ grown by using ICl₃ as a transport agent. This species can be identified as the defect species (SCl)^2-. The similarity and differences exhibited by this defect species in the sulfur-deficient Fe pyrite and the chalcogen-deficient Ru pyrites are discussed.