RESUMEN
The search for intrinsic half-metallic ferromagnetic (FM) monolayers with a high Curie temperature (TC), considerable magnetic anisotropy energy (MAE), and multiferroic coupling is key for the development of ultra-compact spintronics. Here, we have identified a new stable FM Janus monolayer, the tetrahedral CrSSe, through first-principles structural search calculations, which not only exhibits very interesting magnetoelectric properties with a high TC of 790 K, a large MAE of 0.622 meV per Cr, and robust half-metallicity, but also shows obvious ferroelasticity with a modest energy barrier of 0.31 eV per atom. Additionally, there appears to be interesting multiferroic coupling between in-plane magnetization and ferroelasticity. Furthermore, by replacing the Se/S atoms in the CrSSe monolayer with S/Se atoms, we obtained two new half-metallic FM CrS2 and CrSe2 monolayers, which also exhibit excellent magnetoelectric properties. Therefore, our findings provide a pathway to design novel multiferroic materials and enrich the understanding of 2D transition metal chalcogenides.
RESUMEN
Tantalum (Ta) is an interesting transition metal that exhibits superconductivity in its elemental states. Additionally, several Ta chalcogenides (S and Se) have also demonstrated superconducting properties. In this work, we propose the existence of five high-pressure metallic Ta-O compounds (e.g., TaO3, TaO2, TaO, Ta2O, and Ta3O), composed of polyhedra centered on Ta/O atoms. These compounds exhibit distinct characteristics compared to the well-known semiconducting Ta2O5. One particularly interesting finding is that TaO3 shows an estimated superconducting transition temperature (Tc) of 3.87 K at 200 GPa. This superconductivity is primarily driven by the coupling between the low-frequency phonons derived from Ta and the O 2p and Ta 5d electrons. Remarkably, its dynamically stabilized pressure can be as low as 50 GPa, resulting in an enhanced electron-phonon coupling and a higher Tc of up to 9.02 K. When compared to the superconductivity of isomorphic TaX3 (X = O, S, and Se) compounds, the highest Tc in TaO3 is associated with the highest NEF and phonon vibrational frequency. These characteristics arise from the strong electronegativity and small atomic mass of the O atom. Consequently, our findings offer valuable insights into the intrinsic physical mechanisms of high-pressure behaviors in Ta-O compounds.
RESUMEN
Two-dimensional antiferromagnetic (AFM) materials with an intrinsic semiconductivity, a high critical temperature, and a sizable magnetic anisotropy energy (MAE) have attracted extensive attention because they show promise for high-performance spintronic nanodevices. Here, we have identified a new FeCN2 monolayer with a unique zigzag Fe chain through first-principles swarm structural search calculations. It is an AFM semiconductor with a direct band gap of 2.04 eV, a Néel temperature (TN) of 176 K, and a large in-plane MAE of 0.50 meV per Fe atom. More interestingly, the intrinsic antiferromagnetism, contributed by the strong magnetic coupling of neighbouring Fe ions, can be maintained under the external biaxial strains. A large cohesive energy and high dynamical stability favor synthesis and application. Therefore, these fascinating properties of the FeCN2 monolayer make it a promising nanoscale spintronic material.
RESUMEN
Metal phosphides have triggered growing interest for their exotic structures and striking properties. Hence, within advanced structure search and first-principle calculations, several unprecedented Y-P compounds (e. g., Y3 P, Y2 P, Y3 P2 , Y2 P3 , YP2 , and YP3 ) were identified under compression. Interestingly, as phosphorus content increases, P atoms exhibit diverse behaviors corresponding to standalone anion, dumbbell, zigzag chain, planar sheet, crossing chain-like network, buckled layer, three-dimensional framework, and wrinkled layer. Particularly, Fd-3m YP2 can be viewed as assemblage of diamond-like Y structure and rare vertex-sharing tetrahedral P4 â units. Impressively, electron-phonon coupling (EPC) calculations elucidate that Pm-3m Y3 P possesses the highest superconducting critical temperature Tc of 10.2â K among binary transition metal phosphides. Remarkably, the EPC of Pm-3m Y3 P mainly arises from the contribution of low-frequency soft phonon modes, whereas mid-frequency phonon modes of Fd-3m YP2 dominate. These results strengthen knowledge of metal phosphides and pave a way for seeking superconductive transition metal phosphides.
RESUMEN
Exploring new two-dimensional (2D) materials is of great significance for both basic research and practical applications. Although boron can form various 3D and 2D allotropes due to its ease of forming multi-center bonds, the coexistence of honeycomb and kagome boron structures has never been observed in any 2D material yet. In this article we apply first-principle swarm structural searches to predict the existence of a stable MnB5structure, consisting of a sandwich of honeycomb and kagome borophenes. More interestingly, a MnB5nanosheet is a semiconductor with a band gap of 1.07 eV and a high optical absorption in a broad band, which satisfies the requirements of a very good photovoltaic material. Upon moderate strain, MnB5undergoes a conversion from an indirect to a direct band gap semiconductor. The power conversion efficiency of a heterostructure solar cell made of MnB5is up to 18%. The MnB5nanosheet shows a robust dynamical and thermal stability, stemming from the presence of intra- and interlayer multi-center σ and π bonds. These characteristics make MnB5a promising photovoltaic material.
