THE PHASE DIAGRAM OF THE FeGa2Se4-FeIn2Se4 SYSTEM AND THE CRYSTAL STRUCTURE OF FeGaInSe4

Abstract

The compounds of the MB₂X₄ type (M-Mn, Fe, Co, Ni, B-Ga, In, Sb, Bi; X- S, Se, Te) exhibit the phenomenon of electron- or optically-controlled magnetism; therefore, they are very promising for creation of lasers, modulators of light, photodetectors and other magnetic field controllable functional devices. Recent studies have shown that the range of functional characteristics of these compounds can be substantially improved and expanded due the changing the composition of these compounds and the obtaining solid solutions of various types of substitution. The above-mentioned shows the relevance of researches aimed to obtain and study the properties of solid solutions based on the MB₂X₄ compounds.

The development and optimization of processes for the preparation of new complex phases are based on the data on phase equilibria and thermodynamic characteristics of the corresponding system.

The aim of the present study was determining the phase relations in the FeGa₂Se₄-FeIn₂Se₄  system. We used the differential thermal analysis (DTA) and X-ray diffraction (XRD) in order to analyze the samples of the system. The temperatures of the thermal effects were determined using a NETZSCH 404 F1 Pegasus differential scanning calorimeter within room temperature and ~1300 K. The phase composition of the powdered samples was identified by powder X-ray diffraction D2 Phaser diffractometer at room temperature. The definition and refinement of the structure, as well as calculation of the unit cell parameters of intermediate alloys, were carried out by the Rietveld method using Topas- 4.2 software.

It is established that the studied system is quasi-binary, and characterized by the presence of the distectic and eutectic equilibria, as well as the formation of broad areas of solid solutions FeGa₂Se₄ (a-phase) and FeIn₂Se₄ (b-phase). b-phase with composition of FeGaInSe₄ melts congruently at 1222 K and crystallizes in the trigoinal system: Sp.gr. R3m, а = 0.39290(1) nm, с = 3.8542(6) nm, V = 515.28 (15) nm³.

Using the powder diffraction data, the occupation of the crystallographic positions in FeGaInSe₄ was determined by the Rietveld method. It was shown that the occupation of the crystallographic positions in FeGaInSe₄ qualitatively differs from FeIn₂Se₄.

Obtained experimental results can be used for choosing the composition of solution-melt for the growth of the high-quality crystals of intermediate phases which are of interest as magnetic semiconductors.

ACKNOWLEDGMENTS

The work has been carried out within the framework of the international joint research laboratory “Advanced Materials for Spintronics and Quantum Computing” (AMSQC) established between Institute of Catalysis and Inorganic Chemistry of ANAS (Azerbaijan) and Donostia International Physics Center (Basque Country, Spain).