Cu_2(1−z)Mn_zGa₂Se₄ alloys: Phase diagram and effects of Mn ordering on magnetic behaviour

Abstract

X-ray powder diffraction, differential thermal analysis, and magnetic susceptibility measurements on polycrystalline samples are used to determine the details of the T ( z ) phase diagram of the alloy system Cu~(l-,~Mn,Ga$3e~. At high temperatures, there is a single phase solid solution across the complete diagram in a disordered zincblende phase. However, at lower temperatures, the singlephase range is limited to relatively wide terminal fields, which are ordered structures based on a ziricblende subcell. Several different ordered phases are found to occur and the values of the Curie-Weiss constant 8 are used to investigate the changes in ordering with composition. It is shown that these ordering changes cause discontinuous changes in the slope of the graphs against composition of the lattice parameters, optical energy gap, and N8el temperature values.

Magnetic Behaviour for the MnIn2(1—z)Ga2zSe4 Alloys

“…1a, for a sample with z = 0.9, shows a linear 1/c variation with T over the complete range investigated, with a Curie-Weiss q value of À24 K. The curve in Fig. However, as was shown previously [4,8,9] for alloys of similar phase diagrams, the values of the Curie-Weiss constant q determined from magnetic measurements give a good indication of the ordering of the Mn atoms in the lattice. In this case extrapolation of the linear region of the curve gave a value of q of about À100 K. Analysis and Discussion As indicated above, at low temperatures two single-phase solid fields occur.…”

X-Ray Diffraction (XRD), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM) of (CuInSe2)1?x (VSe)x Alloys (0 ?x ? 0.5)

“…(CuGaTe)(CdTe) [1,6,28,45]; (AgInTe 2 )(ZnTe) [18,28] [24,26,43]; (AgInTe 2 )(MnTe) [14,26,42] (CuGaTe 2 )(MnTe) [16] cubic (NaCl) relative short range of solid solubility (CuInSe 2 )(MnSe) [15]; (CuGaSe 2 )(MnSe) [44]; (CuInS 2 )(MnS) [50] hexagonal (W) short range of solid solubility exceptions: relative large single phase field (CuAlS 2 )(CdS), (CuGaS 2 )(CdS), (CuAlS 2 )(CdS), (AgAlS 2 )(CdS), (AgInS 2 )(CdS), (AgAlS 2 )(ZnS), (CuInS 2 )(CdS), (AgGaS 2 )(CdS) [4,28]; (CuGaSe 2 )(CdSe) [25,28]; (AgGaS 2 )(ZnS) [2,28] ; (AgInS 2 )(ZnS) [2,3,28] (CuInSe 2 )(CdSe) [12,28] usually gives samples showing conditions corresponding to equilibrium near room temperature.…”

Magnetic properties for the Mn2GeTe4 compound

“…These studies have been extended to the investigation of the tetrahedrally coordinated I-III-VI 2 , II-III 2 -VI 4 and I 2 -II-IV-VI 4 compounds and alloys [4][5][6]. Another group of semiconducting materials, which would show similar tetrahedrally bounded form, are the II 2 -IV-VI 4 compounds.…”

“…Regarding the olivine structure of II 2 -IV-VI 4 inversion symmetry and four on 4c sites with mirror symmetry, giving various magnetic configurations at low temperature. The magnetic properties of the Mn 2 SiS 4 and Fe 2 GeS 4 have been studied by magnetization and neutron diffraction measurements, and it was found that several different magnetic configurations in succession going from helium to room temperature occur in these compounds [10,11].…”