The European Physical Journal B最新文献

In this work, we present a comprehensive first-principles investigation of a new family of Pt-based half-Heusler alloys with the general formula PtYZ (Y = V, Nb, Ta; Z = Al, Ga, In), all satisfying the 18-valence-electron rule and exhibiting semiconducting behavior. The alloys preferentially crystallize in the type-III structure, fulfilling the Born–Huang mechanical stability criteria, with Pugh’s and Poisson’s ratios indicating ductile and predominantly ionic bonding. Phonon dispersion calculations, performed for representative compounds, further confirm their dynamical stability. The HSE06 hybrid functional significantly refines the electronic description, yielding band gaps from −0.05 to −1.0 eV and revealing a clear trend of increasing d-orbital delocalization from 3d (V) to 5d (Ta) elements. Optical simulations show strong absorption across the visible and ultraviolet regions, with a redshift toward the visible–NIR range for V-based alloys. The combination of mechanical robustness, tunable band gaps, and favorable optical absorption highlights these Pt-based half-Heusler alloys as promising candidates for solar cell and optoelectronic applications, expanding the design space of functional semiconducting Heusler compounds and providing valuable guidance for future experimental studies.

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We investigated the magneto-electronic, structural, mechanical, and thermal properties of a novel family of Ti₂RhX (X = Si, Ge, and Sn) ternary Heusler alloys using the full-potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k code. The results reveal that all compounds are ferrimagnetic with negative formation energies, indicating thermodynamic stability and feasibility for experimental synthesis. Electronic band structure and density of states calculations confirm their half-metallic ferrimagnetic character, with spin polarization near the Fermi level and minority-spin band gaps of approximately 0.1–0.3 eV. Mechanical analysis based on elastic constants shows that these materials are ductile, with high Young’s modulus and Pugh’s ratio exceeding 1.75. Thermal properties were examined using the quasi-harmonic Debye model and non-equilibrium Gibbs functions, yielding temperature- and pressure-dependent trends in heat capacity, bulk modulus, Debye temperature, and thermal expansion coefficients. These findings suggest that Ti₂RhX alloys are promising candidates for spintronic applications and pave the way for further theoretical and experimental investigations.

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We extensively studied Ti2RhX (X = Si, Ge, Sn) Heusler alloys using advanced FP-LAPW methods, unveiling their ferrimagnetic nature, stiffness, and half-metallic ferrimagnetic behavior. Our research also probed their thermal properties and provided a foundational understanding for potential applications.

A machine learning framework has been established to predict the thickness-dependent Spintronic Device characteristics (R_P: Parallel Resistance, R_AP: Antiparallel Resistance, TMR: Tunnel Magnetoresistance (%), STT-IN: In-plane Spin Transfer Torque, STT-OUT: Out of Plane STT) versus voltage behaviour for Organic Magnetic Tunnel Junction (MTJ) devices (x/Rubrene/Co, x = La₂O₃, LaMnO₃, La_0.7Ca_0.3MnO₃, La_0.7Sr_0.3MnO₃). Machine learning (ML) analysis reveals that variation in thickness and interfacial scattering strongly influence spintronic parameters. With proper hyperparameter tuning of the polynomial linear regression and support vector regression model, resistance profiles are well predicted for three MTJs, except La₂O₃. The spin-split band structure of La₂O₃ exhibits a higher density of electronic states near the Fermi level, which modifies the spin-dependent tunnelling behaviour; consequently, spin-flip-related transport requires more complex models. Optimised Gaussian process regression model with multiple kernels not only accurately predicts MTJ TMR responses across voltages and barrier thicknesses but also captures both simple and complex physical relationships arising from different physical effects. In La₂O₃, the ML model fails to capture in-plane and out-of-plane STT responses due to weak magnetic coupling between the electrodes, which abruptly enhances spin-damping compensation with changing barrier thickness. In contrast, varying model complexity in three MTJs, except La₂O₃, provides insights into underlying transport mechanisms, such as spin-flip scattering and spin-damping compensation. Our findings indicate that by leveraging ML approaches, unexplored TMR responses can be predicted for different thickness and voltage settings, when the transport physics of the MTJ are consistent. By utilising simulation and ML models, the study provides significant insights into achieving high TMR for next-generation memory, logic, and quantum technologies. The approach not only enables accurate prediction of MTJ performance but also reduces computational and experimental requirements, whilst simultaneously offering valuable information on device physics after visualising various parameters.

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Cesium fluoride (CsF), a prototypical ionic compound with a wide band gap, is of pivotal importance for numerous technological applications. However, its large band gap hinders its functional integration into optoelectronic devices requiring semiconductor properties. The aim of this work is to present a first-principles investigation of the structural, electronic, and dielectric properties of cubic CsF under hydrostatic pressure, using density functional theory within the generalized gradient approximation. Our findings demonstrate a progressive reduction of the band gap from 5.41 eV at ambient conditions to 2.40 eV at 105 GPa, associated with a transition from an indirect gap at zero pressure to a direct gap at high pressure. Analysis of the density of states reveals enhanced s–p hybridization between Cs 6s, and F 2p orbitals under compression, which drives the electronic evolution. In parallel, we observe a significant alteration of the dielectric properties with pressure. The Born effective charges and the electronic part of the dielectric tensor increase monotonically under compression, whereas the ionic part first decreases and then the trend reverses and grows slowly beyond 25 GPa, reflecting complex changes in lattice dynamics. These outcomes provide new insights into the pressure-dependent behavior of CsF and elucidate the potential of external compression as a tool to tune its electronic and dielectric properties for emerging functional applications.

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