An ESR Investigation of Synthetic Pyrite Crystals

Abstract

Synthetic pyrite crystals doped with halogen (CI, Br) or manganese (Mn) were investigated by ESR at 78 K with an X-band spectrometer and a TE102 cavity with 100 kc field modulation. The crystals were preferably measured with the directions 〈100〉, 〈110〉, and 〈111〉 parallel to the static magnetic field HO. The ESR spectrum of Mn-doped crystals showed a sextet which can be explained by a spin-Hamiltonian for an electron spin S = 1/2 in interaction with the nuclear spin I = 5/2 of the Mn nucleus for axial symmetry. Due to the observed spin and due to the orientation of the paramagnetic centers the spectra were assigned to Mn2+ in the low spin state which resides on cation site in the FeS2, lattice. In halogen-doped crystals four pairs of lines can be interpreted by the interaction of the two isotopes of I = 3/2, 79Br, 81Br and 35Cl, 37Cl, respectively, with an electron spin S = 1/2. According to the observed symmetry of the ESR signals the paramagnetic centers can be explained as (S-X)2- radicals (X = CI, Br) which substitute for the (S2)2- dumb-bells of pyrite. All crystals evoked extremely narrow ESR lines, especially the halogen-doped crystals with linewidths down to 0.03 mT. Excellent agreement between measured and calculated spectra up to the finest details has been obtained.

Thermal conductivity and phonon anharmonicity of chemical vapor transport grown and mineral–FeS2single crystals: An optothermal Raman study

“…[ 57 ] Moreover, electron paramagnetic resonance studies have shown that halogen containing defect species lead to sulfur deficiency such as (SCl) 2− and (SBr) 2 being present in synthetic FeS 2 . [ 58,59 ] Furthermore, the existence of such defects has been evidenced in numerous reports, where the electrical resistivities of those crystals is strongly reduced due to halogen doping. As shown in Table 2, there are two order of magnitude difference between electrical resistivities of the Schönbrunn crystal and the synthetic FeS 2 .…”

Inflexible stoichiometry in bulk pyrite FeS2 as viewed by in situ and high-resolution X-ray diffraction

“…Luck et al (1989) used ICP-AES to show that cystals grown by Fiechter using CVT methods had Br impurities from the transport agent (30-280 mg g À1 ) and P impurities from the sulfur source (170-210 mg g À1 ). Electron spin resonance measurements performed by Siebert determined Br will create Br-S bonds in the FeS 2 lattice (Siebert et al, 1989). Hu calculated that these Br-S bonds act as an n-type dopant in the lattice (Hu et al, 2012).…”

Crystal Growth and Surface Modification of Pyrite for Use as a Photovoltaic Material

“…This has been very popular for pyrite and most of the published data with Vph measurements have been done on CVT samples. 3,5,7,15,19,21,23,30,34,28,35,38,41,43,84,85,87,[90][91][92][96][97][98][99][100]103,27,110,123,[128][129][130][131][132][133][134][135][136][137][138][139][140][141] Unfortunately the halide transport agent is included within the crystal. 35,92 Pyrite also decomposes at 300 °C into iron sulfide and sulfur gas.…”