Dielectric constant and EPR spectra of Fe doped TlInS₂ crystal near the structural phase transitions

Abstract

Dielectric constant and electron paramagnetic resonance (EPR) spectra of Fe-doped TlInS₂ crystal has been investigated in the temperature range of 5–300 K. The influence of Fe impurities on dielectric properties of TlInS₂ crystal has been considered in comparison with earlier observed results from pure TlInS₂ compounds. Considerable decrease of the dielectric constant, as well as the change of the shape of its temperature dependence in a result of influence of doped iron atoms, has been observed. It has been established that EPR lines exhibit remarkable splitting and appearance of additional resonance lines at the temperatures lower than 200 K, which is attributed earlier as the temperature of the ferroelectric phase transition. The simulation for low-temperature EPR spectra has been performed taking into account the appearance of four additional centers in addition to four equivalent centers observed from EPR spectra at room temperature. Such transformations are considered as result of nonequivalent displacements of different groups of Tl atoms during the structural phase transitions.

Keywords:

• electron paramagnetic resonance
• ferroelectrics
• phase transitions
• crystal fields

Acknowledgements

F.A. Mikailor is indebted to Research Projects Commission of Gebze Institute of Technology for supporting this work by the Grant No. 2007-A-14 and to The Scientific & Technological Research Council of Turkey (TÜBİTAK) for supporting by Project. No. 106M540.