EPR study of the structural phase transitions in Fe³⁺ doped TlInS₂

Abstract

The results of low temperature EPR investigations of Fe doped TlInS2 single crystals in the temperature range 5–300 K are presented. The EPR signal due to Fe3+ centers located at the centers of InS4 tetrahedrons has been observed. It has been established that the resonance lines exhibit a slight shift and remarkable splitting at the temperatures lower than 200 K, which is attributed to the effect of the ferroelectric phase transition. The rotational patterns of the resonance fields reveal a doubling of the number of centers at low temperatures. The preliminary simulation indicates that the doubling is related to the rotation of the principal axis system of the centers, while the magnitude of fine structure splitting is nearly the same. ( © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low temperature EPR spectra of Fe3+ centers in ternary layered TlGaS2 crystal

“…Conversely, the preliminary results of our computer simulations of the low temperature EPR spectra of Fe 3+ centers with the spin Hamiltonian in the form (1) indicate no doubling of the resonating centers at low temperatures. This is a very interesting situation, which is opposite to that observed for other compounds isostructural to TlGaS 2 [14,15]. As it was revealed in those works, the observed low-temperature doubling of the number of resonating Fe centers in TlInS 2 and TlGaSe 2 crystals is due to the rearrangement of Tl atoms in the plane of layers, which is accompanied by non-equivalent displacements of two different groups of Tl atoms.…”

“…Additionally, a decrease of the number of resonance lines has been observed on lowering the temperature. Here, one would like to mention about shifts and remarkable splitting and multiplication of the EPR lines observed recently in isostructured TlInS 2 and TlGaSe 2 compounds [14,15], which are mainly evidences for the appearance of the low-temperature structural phase transitions in other representatives of Tl + (M 3+ X 2 )-compounds. The angular variations of the EPR spectra as well as the experimental rotational patterns of the resonance fields are presented in figure 3 and 4.…”

Thermal and EPR investigations of thallium gallium disulphide single crystal

“…In this research the temperature dependence of the heat capacity of TlGaS 2 is studied using DSC technique for the first time. Additionally, the study complements the previously made detailed investigations on EPR of Fe doped TlGaS 2 [10,11], with the temperature dependences of EPR spectra. Here we refer to temperature behaviour of EPR spectra in a wide temperature interval to examine a presence of structural transformations in TlGaS 2 .…”

“…It becomes wider and more intense at 43 K but then its intensity starts to decrease and gets invisible at 180 K. In our previous study [13], we investigated the angular dependence of all these resonance lines and obtained best fit EPR parameters as g= 2.00, D=0.6000 (0.6300) cm However, no temperature-dependent changes peculiar to structural phase transitions have been observed in EPR spectra of Fe doped TlGaS 2 . As it is known from the previous works [10,11,14], such changes take place in EPR spectra of isostructural compounds of TlGaS 2 (TlInS 2 and TlGaSe 2 ) and contain the processes of splitting (between 800-1500 Oe) and multiplication of the resonance lines (triplet) by lowering the temperature and passing through the possible phase transition temperature assigned for those compounds in literature.…”

Behavior of the Switching Effect in P-Type TlInS2 Ternary Chalcogenide Semiconductor

“…TlInS 2 , which is a member of this class of crystals, is a semiconductor with an indirect band gap of about 2.28 eV at room temperature [3] . Some of the physical properties of TlInS 2 , have been investigated by many authors [4][5][6][7][8][9] . The aim of this work is to study the switching phenomenon in Thallium Indium disulphide single crystal in wide range of temperatures as well as light intensity and sample thickness.…”