More Like this

1. Sr(Ag _1−x Li _x ) ₂ Se ₂ and [Sr ₃ Se ₂ ][(Ag _1−x Li _x ) ₂ Se ₂ ] Tunable Direct Band Gap Semiconductors

   https://doi.org/10.1002/anie.202301191  

   Zhou, Xiuquan; Wilfong, Brandon; Chen, Xinglong; Laing, Craig; Pandey, Indra R.; Chen, Ying‐Pin; Chen, Yu‐Sheng; Chung, Duck‐Young; Kanatzidis, Mercouri G. (February 2023, Angewandte Chemie International Edition)

   Abstract Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag_1−xLi_x)₂Se₂layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag_1−xLi_x)₂Se₂withxup to 0.45. In addition, a new type of intergrowth compound [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] was synthesized upon further reaction of Sr(Ag_1−xLi_x)₂Se₂with SrSe. Both Sr(Ag_1−xLi_x)₂Se₂and [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag_1−xLi_x)₂Se₂can be precisely tuned via fine‐tuningxthat is controlled by only the flux ratio and temperature. 

   more » « less
2. Superconductivity and Pronounced Electron‐Phonon Coupling in Rock‐Salt Al _1−x O _1−x and Ti _1−x O _1−x

   https://doi.org/10.1002/aelm.202400141  

   Žguns, Pjotrs; Gedik, Nuh; Yildiz, Bilge; Li, Ju (May 2024, Advanced Electronic Materials)

   Abstract The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb_1−xO_1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al_1−xO_1−xand Ti_1−xO_1−x(λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc_1−xO_1−xand Nb_1−xO_1−xshow significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti_1−x(O_1−xHx) and Nb_1−x(O_1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure. 

   more » « less
3. Medium‐Entropy Engineering of Magnetism in Layered Antiferromagnet Cu _x Ni _{2(1‐ x )} Cr _x P ₂ S ₆

   https://doi.org/10.1002/adfm.202418722  

   Upreti, Dinesh; Basnet, Rabindra; Sharma, M_M; Chhetri, Santosh_Karki; Acharya, Gokul; Nabi, Md_Rafique_Un; Sakon, Josh; Benamara, Mourad; Mortazavi, Mansour; Hu, Jin (December 2024, Advanced Functional Materials)

   Abstract Antiferromagnetic van der Waals‐typeM₂P₂X₆compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions inM₂P₂X₆. Here, we report co‐substitution of Cu¹⁺and Cr³⁺for Ni²⁺in Ni₂P₂S₆, creating Cu_xNi_2(1‐x)Cr_xP₂S₆medium‐entropy alloys spanning a full substitution range (x= 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co‐substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light‐matter interaction and high‐temperature ferroelectricity, can enable multifunctional device applications. 

   more » « less
4. Oxygen Incorporation in the Molecular Beam Epitaxy Growth of Sc _x Ga _1−x N and Sc _x Al _1−x N

   https://doi.org/10.1002/pssb.201900612  

   Casamento, Joseph; Xing, Huili Grace; Jena, Debdeep (January 2020, physica status solidi (b))

   Secondary‐ion mass spectrometry (SIMS) is used to determine impurity concentrations of carbon and oxygen in two scandium‐containing nitride semiconductor multilayer heterostructures: Sc_xGa_1−xN/GaN and Sc_xAl_1−xN/AlN grown by molecular beam epitaxy (MBE). In the Sc_xGa_1−xN/GaN heterostructure grown in metal‐rich conditions on GaN–SiC template substrates with Sc contents up to 28 at%, the oxygen concentration is found to be below 1 × 10¹⁹ cm⁻³, with an increase directly correlated with the scandium content. In the Sc_xAl_1−xN–AlN heterostructure grown in nitrogen‐rich conditions on AlN–Al₂O₃template substrates with Sc contents up to 26 at%, the oxygen concentration is found to be between 10¹⁹and 10²¹ cm⁻³, again directly correlated with the Sc content. The increase in oxygen and carbon takes place during the deposition of scandium‐alloyed layers. 

   more » « less
5. Distinct Composition‐Dependent Topological Hall Effect in Mn _2‐x Zn _x Sb

   https://doi.org/10.1002/apxr.202300145  

   Nabi, Md_Rafique_Un; Li, Yue; te_Velthuis, Suzanne_G_E; Chhetri, Santosh_Karki; Upreti, Dinesh; Basnet, Rabindra; Acharya, Gokul; Phatak, Charudatta; Hu, Jin (February 2024, Advanced Physics Research)

   Abstract Spintronics, an evolving interdisciplinary field at the intersection of magnetism and electronics, explores innovative applications of electron charge and spin properties for advanced electronic devices. The topological Hall effect (THE), a key component in spintronics, has gained significance due to emerging theories surrounding noncoplanar chiral spin textures. This study focuses on Mn_2‐xZn_xSb, a material crystalizing in centrosymmetric space group with rich magnetic phases tunable by Zn contents. Through comprehensive magnetic and transport characterizations, we found that the high‐Zn (x > 0.6) samples display THE which is enhanced with decreasing temperature, while THE in the low‐Zn (x < 0.6) samples show an opposite trend. The coexistence of those distinct temperature dependencies for THE suggests very different magnetic interactions/structures for different compositions and underscores the strong coupling between magnetism and transport in Mn_2‐xZn_xSb. The findings contribute to understanding topological magnetism in centrosymmetric tetragonal lattices, establishing Mn_2‐xZn_xSb as a unique platform for exploring tunable transport effects and opening avenues for further exploration in the realm of spintronics. 

   more » « less