Chalcogenide Spinels Research Articles

Computational study of Cd-based chalcogenide spinels CdSm2(S/Se)4 for spintronic applications

In this letter, first-principle computations are utilized in order to explore the Cd-based chalcogenide spinels CdSm2(S/Se)4 spinels. Generalized gradient approximation (PBEsolGGA) and modified Becke-Johnson potential (mBJ) are used to calculate structural, mechanical, spin-polarized electronic and magnetic features. The optimization analysis demonstrates that ferromagnetic contends of both chalcogenides releases a greater amount of energy than the anti-ferromagnetic contends. Further, structural and thermodynamic stability are justified through the calculations Born stability criteria and formation energy. Additionally, mechanical features indicate both chalcogenides are ductile in nature through calculations of Poisson's and Pugh ratios. Curie temperature (Tc) in terms of Heisenberg simulation and the corresponding density of states is also calculated for ferromagnetic stability of both chalcogenides. Spin polarized electrical characteristics that are spin-polarized are indicative of a half-metallic ferromagnetic nature (spin-down indicates the semiconductor nature, while the spin-up is metallic nature). Total magnetic moments of both chalcogenides are appear due to hybridization of f-states of rare earth (Sm) element and p-states of chalcogenides.

To Be or Not to Be – Is MgSc2Se4 a Mg‐Ion Solid Electrolyte?

AbstractMagnesium batteries offer promising potential as next‐generation sustainable energy‐storage solutions due to the high theoretical capacity of the magnesium metal anode. Facilitating dendrite‐free operation of metal anodes necessitates the development of solid electrolytes with high magnesium‐ion conductivity. While the chalcogenide spinel MgSc2Se4 is predicted to exhibit high magnesium ion mobility, unequivocal experimental evidence for magnesium ion conduction beyond short‐range motion is still missing. This study confirms magnesium‐ion transport in MgSc2Se4 through two independent electrochemical methods: electrochemical deposition of magnesium metal and reversible magnesium plating/stripping cycling. To overcome the difficulty of measuring the ionic conductivity of the mixed conducting MgSc2Se4 spinel, a pure ion conducting interlayer is employed in a symmetric transference cell. This approach effectively suppresses the electron transport, allowing accurate characterization of the ionic conductivity. The experimental results confirm a low migration barrier of (386 ± 24) meV for magnesium ion transport in MgSc2Se4 and demonstrate one of the best performances at room temperature among the reported inorganic magnesium solid electrolytes. The findings open a new door for exploring additional mixed magnesium ion conductors and highlight the potential of magnesium chalcogenide spinels as a promising class of magnesium solid electrolytes.

MgSc2Se4 Solid Electrolyte for Rechargeable Mg Batteries: An Electric Field‐Assisted All‐Solid‐State Synthesis

Magnesium scandium chalcogenide spinels are an important class of materials in Mg anode‐based batteries for energy storage applications. The applications of these intriguing materials are not limited to the energy storage, but the use of these materials may also be useful in solar cells, owing to the material optical bandgap. So far, all reported synthetic routes for these spinels involve high‐temperature furnace treatment. Herein, a process which involves a facile electric field‐assisted synthesis of MgSc2Se4 is reported on, yielding after a very short thermal treatment, a material possessing a low room‐temperature electronic conductivity of ≈10−11 S cm−1, and a room‐temperature Mg‐ion conductivity of 1.78 × 10−5 S cm−1. The crucial role of extra selenium on the material electronic conductivity is discussed and explained in detail.

Ferromagnetic Cd(1-x)CuxCr2S4 thin films: Synthesis, characterization, and first-principles calculations

The magnetic chromium-based chalcogenide spinel system has been proposed for development of a new class of spintronic devices. They have been extensively investigated because of their unique electrical, magnetic, and optical properties. For example, CdCr2S4 is a well-established ferromagnetic semiconductor, while CuCr2S4 is a ferromagnetic metal. Their solid solution, Cd(1-x)CuxCr2S4, offers an exciting possibility to tailor the magnetic and optical properties. In bulk form, they exhibit ferrimagnetic ordering with Curie temperature of about 85 K (for x = 0.1). However, thin films of these mixed magnetic chalcospinels materials have not been investigated. We have deposited Cd(1-x)CuxCr2S4 thin films using a versatile and simple chemical spray deposition (CSD) method combined with post-annealing in a sulfur atmosphere. The Cd(1-x)CuxCr2S4 thin films are deposited over a range of 0 ≤ x ≤ 0.2 using simple inorganic salts of Cd, Cu, and Cr. Systematic changes in the unit cell volume, lattice parameter, bandgap, and magnetic properties are observed with Cu incorporation. A decrease in the saturation magnetic moment and transition temperature (Tc) are noted with increasing Cu substitution. First principles spin-polarized calculations within GGA and PBE approximation have been performed to determine the electronic and magnetic structure as a function of composition. The results suggest that an antiparallel alignment between Cu and Cr spins decreases the magnetization with increasing Cu substitution. The theoretical results are in qualitative agreement with the experimental findings and highlight the development of Cd(1-x)CuxCr2S4 (0 ≤ x ≤ 0.2) thin films with tunable magnetic and semiconducting properties.

The Zn1-xPbxCr2Se4-Single Crystals Obtained by Chemical Vapour Transport-Structure and Magnetic, Electrical, and Thermal Properties.

Monocrystalline chalcogenide spinels ZnCr2Se4 are antiferromagnetic and semiconductor materials. They can be used to dope or alloy with related semiconducting spinels. Therefore, their Pb-doped display is expected to have unique properties and new potential applications. This paper presents the results of dc and ac magnetic measurements, including the critical fields visible on the magnetisation isotherms, electrical conductivity, and specific heat of the ZnCr2S4:Pb single crystals. These studies showed that substituting the diamagnetic Pb ion with a large ion radius for the Zn one leads to strong short-range ferromagnetic interactions in the entire temperature range and spin fluctuations in the paramagnetic region at Hdc = 50 kOe.

Synchronous Control of Transmitted and Reflected Light in Chromium Chalcogenide Spinel Semiconductors

Synchronous Control of Transmitted and Reflected Light in Chromium Chalcogenide Spinel Semiconductors

Investigation of Rare-Earth Chalcogenide Spinel for Mg Solid State Conductors

Magnesium batteries hold potential for overcoming the safety and energy density limitations faced by Li-ion batteries. However, the development of Mg battery technology is plagued by the poor kinetics of Mg transport in solid state materials. Recently, the chalcogenide spinel structure was found to be suitable for rapid Mg2+ diffusion.[1] Based on this result we engaged in a more elaborate study of chalcogenide spinels. Seven stable MgLn2X4 (Ln = lanthanoid, X = S, Se) spinels were evaluated with density functional theory to have low barriers for Mg migration (<380 meV) and reasonable stability. Two of these materials have been synthesized and studied experimentally. We will show how the conductivity can be systematically improved by judicious choice of metal ions. In particular, the effect of large rare-earth cations on expanding the triangular anion bottleneck to reduce the migration barrier and the structure disorder phenomenon will be discussed.Reference: [1] Canepa, P., Bo, S., Sai Gautam, G. et al. High magnesium mobility in ternary spinel chalcogenides. Nat. Commun. 8, 1759 (2017).

Computational investigation of chalcogenide spinel conductors for all-solid-state Mg batteries

Seven MgLn2X4 (Ln = lanthanoid, X = S, Se) spinels are calculated with density functional theory to have low barriers for Mg migration (<380 meV) and are stable or nearly stable (within 50 meV per atom of stability with respect to competing structures and compositions). As the size of the Ln increases, Mg mobility is found to increase, but stability in the spinel structure is found to decrease.

TDPAC Studies of Local Defects and Phenomena in Ferroics and Multiferroics

We provide an overview of time-differential perturbed angular correlation (TDPAC) measurements of ferroic and multiferroic materials. Here, we explore chalcogenide spinels, lead titanate, lead zirconate, and bismuth ferrite, describing the use of TDPAC experiments to probe the physics of localized defects and the various mechanisms that govern electronic and magnetic interactions, the coupling of the associated degrees of freedom, and the structural, charge, and orbital correlations for these materials.

Mössbauer study of non-stoichiometric FeCr2S4 system

A partial spin transition stimulated by spontaneous symmetry breaking has been observed, for the first time, in the non-stoichiometric chalcogenide spinel FeCr2S4. A Fe2+ high spin - low spin transition HS-LS: S = 2 → S = 0 is detected below the Néel temperature TN in the magnetic subsystem corresponding to a part of the sample with deviations from stoichiometry. The fraction of diamagnetic Fe atoms increases with decreasing temperature.

Synthesis, Formation Mechanism, and Magnetic Properties of Monodisperse Semiconducting Spinel CdCr2S4 Nanocrystals via a Facile “Seed-Mediated” Growth Method

The chalcogenide spinel CdCr2S4 is a well-established ferromagnetic semiconductor that exhibits unique properties and is a promising candidate for spintronic applications. With band gap in the visible wavelength region, CdCr2S4 nanocrystals offer the exciting possibility of tailoring both the optical and magnetic properties with precise morphology control. However, the synthesis of monodisperse CdCr2S4 nanocrystals is challenging and has not been reported. A unique “seed-mediated” growth process has been developed for the synthesis that involves using cubic-phase CdS, which has a face-centered cubic crystal structure similar to that of CdCr2S4, as a “seed” to react with CrCl3·6H2O in a solution mixture of 1-dodecanethiol and 1-octadecene. Remarkably, hexagonal-phase CdS is ineffective as a “seed” for formation of the desired product. A mechanism for formation of monodisperse CdCr2S4 nanocrystals by the selective growth process is proposed, and the structural and magnetic properties of the synthesized nanocrystals are presented. The novel synthetic strategy can be exploited for the controlled formation of other complex magnetic chalcogenides.

High magnesium mobility in ternary spinel chalcogenides

Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. The development of a competitive magnesium battery is plagued by the existing notion of poor magnesium mobility in solids. Here we demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01–0.1 mS cm–1 at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door for the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.

Role of Point Defects in Spinel Mg Chalcogenide Conductors

Close-packed chalcogenide spinels, such as MgSc$_2$Se$_4$, MgIn$_2$S$_4$ and MgSc$_2$S$_4$, show potential as solid electrolytes in Mg batteries, but are affected by non-negligible electronic conductivity, which contributes to self-discharge when used in an electrochemical storage device. Using first-principles calculations, we evaluate the energy of point defects as function of synthesis conditions and Fermi level to identify the origins of the undesired electronic conductivity. Our results suggest that Mg-vacancies and Mg-metal anti-sites (where Mg is exchanged with Sc or In) are the dominant point defects that can occur in the systems under consideration. While we find anion-excess conditions and slow cooling to likely create conditions for low electronic conductivity, the spinels are likely to exhibit significant $n$-type conductivity under anion-poor environments, which are often present during high temperature synthesis. Finally, we explore extrinsic aliovalent doping to potentially mitigate the electronic conductivity in these chalcogenide spinels. The computational strategy is general and can be easily extended to other solid electrolytes (and electrodes) to aid in the optimization of the electronic properties of the corresponding frameworks.

Frustrated magnetism in the Heisenberg pyrochlore antiferromagnets AYb2X4 ( A=Cd , Mg; X=S , Se)

Our polycrystalline sample study on the Yb-based chalcogenide spinels $A$Yb$_2$$X_4$ ($A =$ Cd, Mg, $X =$ S, Se) has revealed frustrated magnetism due to the antiferromagnetically coupled Heisenberg spin on the pyrochlore lattice. Our crystal electric field analysis indicates the Yb ground state has nearly Heisenberg spins with a strong quantum character of the ground doublet. All the materials exhibit an antiferromagnetic order at 1.4-1.8 K, much lower temperature than the antiferromagnetic exchange coupling scale of $\sim 10$ K. The magnetic specific heat $C_{\rm M}$ shows a $T^{3}$ dependence, indicating the gapless feature in the Yb-based chalcogenide spinels. The magnetic entropy change much smaller than $R$ ln 2 below the N\'{e}el temperature and the small local magnetic field estimated from the $\mu$SR measurements strongly suggest the significantly reduced size of the ordered moment in comparison with the bare moment size 1.33 $\mu_{\rm B}$/Yb supporting strong fluctuations in the commensurate and incommensurate ordered states in CdYb$_2$S$_4$ and MgYb$_2$S$_4$, respectively.

Semiconducting-metallic transition of singlecrystalline ferromagnetic Hf-doped CuCr2Se4 spinels

Chalcogenide spinels show a variety of physical properties and are very good candidates for electronic and high-frequency applications. We report the measurements of magnetic susceptibility, magnetic isotherm, electrical conductivity, thermoelectric power and calculations of the superexchange and double-exchange integrals made for singlecrystalline Cu[CrxHfy]Se4 spinels. The results showed a ferromagnetic order of magnetic moments below the Curie temperatures of 390K and, an increase in the splitting of the zero-field cooled and field cooled susceptibilities with increasing Hf-content below the room temperature suggesting a slight spin-frustration and a rapid transition from semiconducting to metallic state at room temperature. A quantitative evaluation of the exchange Hamiltonian showed that the total hopping integral rapidly decreased and the bandwidth of the 3d t2g band due to Cr3+ and Cr4+ ions strongly narrowed from 0.76eV for y = 0 to 0.28eV for y = 0.14. The narrowing of this band appears to be responsible for semiconducting properties of the Hf-doped CuCr2Se4 spinels below the room temperature.

The in-plane ferromagnetic ordering in half-metallic CuCr2 Se4−x Brx (x = 0.25) single crystal

The transport property of chalcogenide spinel CuCr2 Se4 with an itinerant ferromagnetic ground state can be modulated by doping of bromine, where the half-metallic state can be realized around x = 0.25 in CuCr2 Se4−x Brx system. In this work, the single crystal CuCr2 Se4−x Brx (x = 0.25) with the cleave surface (111) plane has been investigated by the electron paramagnetic resonance (EPR) spectroscopy. The EPR results show that the in-plane magnetization is strong while the out-of-plane one is weak, which indicate that the spins are ferromagnetic ordered within the (111) plane. In addition, the isothermal EPR spectra in the ferromagnetic phase display that the spin coupling strength (λ) and crystal field (ΔCF) depend on the rotation angle φ as relation λ/ΔCF ∝ cos φ. Moreover, the peak-to-peak linewidth ΔHPP increases linearly with the decrease of temperature, which suggests that the spin-orbit coupling is enhanced linearly with temperature cooling.

Structural transition in the magnetoelectricZnCr2Se4spinel under pressure

Τhe magnetoelectric $\mathrm{ZnC}{\mathrm{r}}_{2}\mathrm{S}{\mathrm{e}}_{4}$ spinel, with space group $Fd\overline{3}m$, undergoes a reversible first-order structural transition initiating at 17 GPa, as revealed by our high-pressure x-ray diffraction studies at room temperature. We tentatively assign the high-pressure modification to an $A\mathrm{M}{\mathrm{o}}_{2}{\mathrm{S}}_{4}$-type phase, a distorted variant of the monoclinic $\mathrm{C}{\mathrm{r}}_{3}{\mathrm{S}}_{4}$ structure. Furthermore, our Raman investigation provides evidence for a pressure-induced insulator-metal transition. Our density functional theory calculations successfully reproduce the structural transition. They indicate significant band gap and magnetic moment reduction accompanying the pressure-induced structural modification. We discuss our findings in conjunction with the available high-pressure results on other Cr-based chalcogenide spinels.

Magnetic phase diagram of (1–x)CuCr1.5Sb0.5S0.5Se3.5–x CuCr2S0.5Se3.5 solid solutions

in studies of the CuCr2S4-CuCr1.5Sb0.5S4 solidsolu� tion series, where the endmembers of the system are the thiochromite CuCr2S4 (ferromagnet with ТС = 367 K) and florencovite, CuCr1.5Sb0.5S4 (antiferro� magnet with TN = 23.8 K). Antimony substitution for chromium in these compounds yields a continuous series of CuCr 2- x Sb x S 4 solid solutions, whose mag� netic properties range from ferromagnetic (x = 0) to antiferromagnetic (x = 0.5), with spin glass as an inter� mediate phase, and which exhibit metallic to semi� conducting behavior of electrical conductivity. By analogy with CuCr 1.5 Sb 0.5 S 4 (5), Aminov et al. (6, 7) synthesized new antiferromagnetic semiconduc� tors with the general formula CuCr1.5Sb0.5S 4- xSex with the aim of creating new spintronic materials based on these solid solutions and containing microregions with an increased degree of ferromagnetic order. Single� phase samples were obtained at х = 0, 0.5, 3.5, and 4, which corresponded to the compounds CuCr1.5Sb0.5S4, CuCr1.5Sb0.5S3.5Se0.5, CuCr1.5Sb0.5S0.5Se3.5, and CuCr 1.5 Sb 0.5 Se 4 . All of the mixed selenide and sul� foselenide chromites containing 0.5 antimony atoms per formula unit were inhomogeneous magnetic mate� rials and transformed on cooling first from their para� magnetic state to spin glass (with a spin freezing tem� perature T f = 37-47 K) and then to an antiferromag� netic state with Neel temperatures TN = 21-30 K. The paramagnetic Curie temperature θp ranged from ⎯104 K at х = 0 to +34.8 K at х = 4. Note that, inde� pendent of the sign and magnitude of θp, all of the CuCr 1.5 Sb 0.5 S 4 - x Se x materials were antiferromagnets at 5 K, as evidenced by the linear magnetic field dependence of their magnetization. Abstract—CuCr1.5 + xSb0.5 - xS0.5Se3.5 (x = 0-0.5) mixed chromium chalcogenide spinels have been synthe� sized for the first time. Their magnetic properties have been studied, their magnetic transformations have been identified, and the magnetic phase diagram of the solid solution system has been mapped out. The CuCr2S0.5Se3.5�based ferromagnetic materials have the largest phase field in the system (0.23 ≤ x < 0.5). With decreasing temperature, the materials undergo a reentrant transition to a spin glass state. In the composition range 0.12 ≤ x ≤ 0.23, the transition to a spin glass state occurs from the paramagnetic region. The antiferro� magnetic materials have the smallest phase field (0 ≤ x ≤ 0.12).

ChemInform Abstract: Giant Magnetotransmission and Magnetoreflection in Ferromagnetic Materials

AbstractReview: such as chromium chalcogenide spinel, manganites with perovskite structure, anthin‐film metallic nanostructures; 64 refs.

Giant magnetotransmission and magnetoreflection in ferromagnetic materials

We present a brief review on magnetotransmission (magnetoabsorption) and magnetoreflection of natural (unpolarized) light in ferromagnetic chromium chalcogenide spinel, manganites with perovskite structure and thin-film metallic nanostructures in the middle infrared spectral range. The magnetooptical effects under discussion are of high interest for numerous and promising applications in the infrared optoelectronics.