First-principles Calculations Research Articles

Pressure-induced anomaly of transport properties and structural transition in layered ferromagnetic metal TlCo2S2

In this work, the structural and transport properties of ferromagnetic metal TlCo2S2 with ThCr2Si2-type crystal structure are systematically studied using high-pressure synchrotron x-ray powder diffraction, electrical transport measurements and first-principles calculations. All the resistances of TlCo2S2 between 1.4 GPa and 5.2 GPa exhibit an upturn at TS and an obvious hysteresis is observed below TS when measured in the cooling and heating processes. As the pressure increases, TS gradually increases and the resistances display a metallic behavior without any anomaly in the whole temperature region above 5.2 GPa, indicating that a possible structural phase transition occurs at TS and is beyond the room temperature above 5.2 GPa. High-pressure x-ray diffraction measurements combined with crystal structure prediction indicate that at room temperature TlCo2S2 undergoes a structural phase transition from a tetragonal phase (I4/mmm) to an orthorhombic structure (Bmab) at Pc ≈6.8 GPa, which is consistent with the results of the resistances under high pressure. Our results indicate that a first-order structural phase transition of TlCo2S2 is induced by high pressure and then results in the anomaly of the electrical transport properties.

Effect of transition metals (Fe, Ru and Os) on the elastic, thermodynamic, electronic, magnetic and thermoelectric properties of three Nd-filled arsenide skutterudites based on first-principles computations

Elastic, electronic, magnetic, thermodynamic, and thermoelectric properties of three neodymium-filled skutterudites NdT4As12 (T = Fe, Ru and Os) have been investigated using density functional theory. The bulk moduli increase with the atomic numbers of the transition metals. All materials are stiff, while the Os compound is the stiffest. A considerable ionic contribution is seen in their inter-atomic bonding. The Fe compound possesses the highest Debye temperature, while the Os compound has the highest melting temperature. GGA+U formalism predicts the semimetallic nature of all the compounds, but their total DOS differs near the Fermi level in both spin channels. The contributions of the Nd-f and T-d electrons differ in the three compounds and two methods. GGA+U predicts the highest magnetic moment in the Fe compound, followed by the Ru and Os compounds. The thermoelectric figure of merit shows no systematic variation with z of the transition metals and in the high temperature region it increases with temperature pretty fast. The highest value of ZT is 0.32 in the Ru compound in the spin-down channel while it is 0.24 in the spin-up channel in the Fe compound, both at 1000 K.

First-principles study on the failure and doping strengthening mechanisms at the interface of high-alumina ferritic heat-resistant steel/oxide film

This study employs first-principles calculations based on density functional theory to explore the failure mechanisms and enhancement strategies for the interface between high-aluminum ferritic heat-resistant steel and oxide film (α-Fe/Al₂O₃ interface). Establishing an interface model at the lowest-energy densely packed plane and performing tensile tests determined that fracture behavior manifests as ductile fracture at the interface. Further analysis of the charge density and differential charge density maps for various doped models confirmed the feasibility of strengthening the α-Fe/Al₂O₃ interface structure through alloy element doping. The results demonstrate that effective dopant elements (such as V, Mn, and Mo) can induce more electrons to transfer to the interface, increase electron concentration, and alter the chemical bonding nature of the interface, thereby significantly enhancing its bonding performance. This study proposes a method to enhance the interface of high-aluminum ferritic heat-resistant steel through doping, providing a theoretical foundation for further research on similar heat-resistant steel surfaces with Al₂O₃ films.

The incorporation of armchair and zigzag boron nitride nanoribbons in graphene monolayers: An examination of the structural, electronic, and magnetic properties

The opening of an energy gap and generating magnetism in graphene are certainly the most significant and urgent topics in your current research. The majority of proposed applications for it require the ability to modify its electronic structure and induce magnetism in it. Here, using first-principles calculations utilizing the PBE and HSE06 functionals, we examine the structural, energetic, electronic, magnetic, and phonon transport characteristics of armchair graphene and boron nitride nanoribbons (aGNRs and aBNNRs), and zigzag graphene and boron nitride nanoribbons (zGNRs and zBNNRs) with varying widths. We shall emphasize the impact of incorporating aBNNRs and zBNNRs of varying widths into graphene monolayers (GMLs). The findings suggest that zBNNRs are easier to insert into GMLs than aBNNRs. A study of the average formation energies of graphene and boron nitride nanoribbons reveals that BNNRs have a formation energy that is at least twenty times greater than GNRs. We have observed energy gaps that can be classified into three distinct families in aGNRs, aBNNRs, and aBNNRs inserted into GML. In the zGNRs and zBNNRs inserted in GML, depending on the width, different magnetic orderings (antiferromagnetic, ferrimagnetic, and ferromagnetic), and electronic behaviors are observed (metallic, semimetallic, semiconductor, and topological insulator).

Design of spintronic devices based on adjustable half-metallicity induced by electric field in A-type antiferromagnetic bilayer NiI2

Exploring the attainment of half-metallic behavior in two-dimensional (2D) materials through external perturbations is a popular area of current research. In this work, we demonstrate, using first-principles calculations, that bilayer NiI2 (bi-NiI2) is an A-type antiferromagnetic (AFM) semiconductor with an indirect bandgap of 0.86 eV, with the most stable configuration being the AB stacking mode. Upon the application of a vertical electric field, the material transforms from its original semiconducting state into a half-metallic state. Moreover, the spin polarization reverses its orientation whenever the direction of the electric field is altered. This intriguing behavior has inspired us to design a spintronic device based on the A-type AFM bi-NiI2. By employing nonequilibrium Green's function (NEGF) combined with density functional theory (DFT) calculations, we find that the device achieves ON/OFF switching by applying vertical electric fields in parallel or anti-parallel configurations in the two leads. The device displays 100 % spin polarization in the parallel configuration (PC) scenario, driven by bias voltage or temperature differences. Utilizing either the parallel or antiparallel configuration (APC) for ON/OFF switching enables the device to exhibit tunneling magnetoresistance (TMR) of up to 1.45 × 1010 % due to bias voltage and up to 1011 % thermal TMR arising from temperature differences between the leads. These findings highlight the potential of NiI2 and A-type AFM bilayers in the design of spintronic devices.

Exploring Mo2B MBene as a high-capacity anode material for multi-valent metal-ion batteries: Insights from first-principles calculations

A novel class of 2-dimensional (2D) materials, known as MBenes, has recently been proposed as a promising candidate for electrode applications in metal-ion batteries due to their high conductivity and rich chemistry. In this study, we present a computational investigation into the potential of Mo2B MBene as an anode material for Na-, Mg-, and Al-ion batteries. Using density functional theory (DFT) calculations, we examine the structural, electronic, and electrochemical properties of both H- and T-type configurations of Mo2B. Our findings reveal that Mo2B exhibits metallic behavior and excellent metal adsorption characteristics, with Al exhibiting the strongest binding affinity, followed by Mg and Na. This strong binding, especially with Al, although results in higher diffusion barriers, it enhances layer adsorption leading to increased theoretical capacity. The calculated maximum capacities are significant, with Al (1323 mAh g−1) showing the highest capacity, followed by Mg (923 mAh g−1) and Na (216 mAh g−1). Additionally, the open-circuit voltage (OCV) for all metals ranges between 0.1 and 1.0 V, suggesting the suitability of Mo2B MBene as an anode material that minimizes dendrite formation risks. These results indicate the potential of Mo2B for high-performance multi-valence ion batteries, with particular promise for Al-ion batteries due to their superior capacity. Furthermore, we propose that strain engineering could optimize Mo2B for enhanced performance in Na-ion batteries. Overall, this study suggests Mo2B MBene as a highly promising anode material for next-generation metal-ion batteries, offering significant advantages in terms of capacity, voltage, and safety. Our findings provide insights that could be used for further experimental design of Mo2B-based anodes for energy storage technologies.

Entropy-Stabilized Multication Fluorides as a Conversion-Type Cathode for Li-Ion Batteries-Impact of Element Selection.

Metal fluorides (e.g., FeF2 and FeF3) have received attention as conversion-type cathode materials for Li-ion batteries due to their higher theoretical capacity compared to that of common intercalation materials. However, their practical use has been hindered by low round-trip efficiency, voltage hysteresis, and capacity fading. Cation substitution has been proposed to address these challenges, and recent advancements in battery performance involve the introduction of entropy stabilization in an attempt to facilitate reversible conversion reactions by increasing configurational entropy. Building on this concept, high entropy fluorides with five cations were synthesized by using a simple mechanochemical route. In order to examine the impact of element selection, Co0.2Cu0.2Ni0.2Zn0.2Fe0.2F2 (HEF-Fe) was compared with Co0.2Cu0.2Ni0.2Zn0.2Mg0.2F2 (HEF-Mg), replacing electrochemically inactive Mg with Fe as an active participant in the conversion reaction. Combining electrochemical measurements with first-principles calculations, high-resolution electron microscopy, and synchrotron X-ray analysis, HEFs' battery performances and conversion reaction mechanisms were investigated in detail. The results highlighted that replacement of Mg with Fe was beneficial, with enhanced capacity, rate capability, and surface stability. In addition, it was found that HEF-Fe showed similar cycle stability without an electrochemically inactive element. These findings provide valuable insights for the design of high entropy multielement fluorides for improved Li-ion battery performance.

Sr-Doping-Modulated Metal-Insulator Transition in NdNiO3 Epitaxial Films

Abstract Perovskite-structured nickelates, ReNiO3 (Re = rare-earth), have long garnered significant research interest due to their sharp and highly tunable metal-insulator transition (MIT). Doping the parent compound ReNiO3 compound with alkaline earth metal can substantially suppress this MIT. Recently, intriguing superconductivity has been discovered in doped infinite-layer nickelates (ReNiO2), while the mechanism behind A-site doping-suppressed MIT in the parent compound ReNiO3 remains unclear. To address this question, we grew a series of Nd1-x Sr x NiO3 (x = 0 ~ 0.2) thin films and conducted systematic electrical transport measurements. Our resistivity and Hall measurements suggest that Sr-induced excessive holes is not the primary reason for MIT suppression. Instead, first-principles calculations indicate that Sr cations, with larger ionic radius, suppress breathing mode distortions and promote charge transfer between oxygen and Ni cations. This process weakens Ni-O bond disproportionation and Ni2+/Ni4+ charge disproportionation. Such significant modulations in lattice and electronic structure convert the ground state from a charge-disproportionated antiferromagnetic insulator to a paramagnetic metal, thereby suppressing the MIT. This scenario is further supported by the weakened MIT observed in the tensile-strained NSNO/STO(001) films. Our work reveals the A-side doping-modulated electrical transport of perovskite nickelate films, providing deeper insights into novel electric phases in these strongly correlated nickelate systems.

Robust topological insulating property in C2X-functionalized III-V monolayers

Two-dimensional topological insulators (TIs) show great potential applications in low-power quantum computing and spintronics due to the spin-polarized gapless edge states. However, the small bandgap limits their room-temperature applications. Based on first-principles calculations, a series of C2X (X = H, F, Cl, Br and I) functionalized III-V monolayers are investigated. The nontrivial bandgaps of GaBi-(C2X)2, InBi-(C2X)2, TlBi-(C2X)2and TlSb-(C2X)2are found to between 0.223 and 0.807 eV. For GaBi-(C2X)2and InBi-(C2X)2, the topological insulating properties originate from thes-px,yband inversion induced by the spin-orbital coupling (SOC) effect. While for TlBi-(C2X)2and TlSb-(C2X)2, the topological insulating properties are attributed to the SOC effect-induced band splitting. The robust topological characteristics are further confirmed by topological invariantsZ2and the test under biaxial strain. Finally, two ideal substrates are predicted to promote the applications of these TIs. These findings indicate that GaBi-(C2X)2, InBi-(C2X)2, TlBi-(C2X)2and TlSb-(C2X)2monolayers are good candidates for the fabrication of spintronic devices.

A-C/Au Film with Low Humidity Sensitivity of Friction by Forming Au Transfer Film.

Amorphous carbon is recognized as an excellent lubricating material; however, its tribological properties are significantly influenced by humidity. To elucidate the mechanism underlying this humidity dependence and to propose a novel enhancement method, we investigated and compared the tribological properties of hydrogenated amorphous carbon (a-C:H) and amorphous carbon/gold (a-C/Au) composite films. First, the friction coefficient of these carbon films under different humidity conditions was tested using a rotational ball-on-disk tribometer. Subsequently, we analyzed the morphology and structure of the sliding interface employing optical microscopy (OM), Raman spectroscopy, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Finally, first-principle calculations were carried out to calculate the adsorption energy of water molecules on different surfaces. The results indicate that the friction coefficient of a-C:H film and the area of transfer film increase with the increase of humidity. This phenomenon can be attributed to the fact that water molecules enhance the interaction between the a-C:H film and steel counterfaces. Notably, in contrast, the friction coefficient of a-C/Au film demonstrates low sensitivity to humidity due to the formation of an Au transfer film that exhibits weak interaction with water molecules. These findings provide a promising strategy for developing environment-adaptive amorphous carbon films and play an important role in promoting the development of intelligent lubricating film.

The influence of carbon content to the band gap of ABC stacked trilayer hybridized graphene and hexagonal boron nitride

The influence of carbon content on the band gap of ABC stacked trilayer hybridized graphene and hexagonal boron nitride (h-BNC) are calculated by first-principles calculations. The formation energy results indicate that the configurations with cluster of boron(B) and nitrogen(N) atoms are more stable than that with separate. By calculating the band structures of seven doping models, we found that the band gap reduces with the ascendance of carbon atom concentration. With the increase of the carbon atom content, the optical absorption peak shifts to longer wavelength range. Combined with the band structure results, the red-shift is due to the reduction of the bandgap with the increase of the carbon atom content. The density of states, charge densities and Mulliken populations suggest that the collapse of the band gap is attributed to the charge transfer between atoms in the seven doping models of the h-BNC system. This work is valuable for the band structure engineering of h-BNC.

Compositional optimization for enhanced oxidation resistance of high-entropy carbide ceramics

Excellent oxidation resistance is essential for the viability of high-entropy carbides (HECs) in high-temperature environments. However, the vast HEC compositional space presents a significant challenge in developing desirable formulations with improved oxidation tolerance. In this work, we establish a computational framework to guide the optimization of oxidation-tolerant HEC compositions and further validate the theoretical predictions through systematic oxidation experiments. Leveraging first-principles calculations, we initially determine the heterogeneous oxygen adsorption ability of different constituent elements in HECs, which is subsequently harnessed to regulate preferential oxidation and suppress the formation of detrimental oxides during the oxidation process. Incorporating this fundamental-level understanding, multi-objective optimization (MOO) was performed to identify a compositional region with potentially intrinsic oxidation immunity, achieving a balance between the compactness of the oxidation product and the thermodynamic stability of the HEC matrix. Based on our analysis, we propose a compositional design strategy involving the strategic reduction of elements with higher oxygen adsorption energies, such as Nb, Ta, and Ti in (NbTaZrHfTi)C, to effectively improve the oxidation performance of HECs. The theoretical findings are robustly corroborated by our comparative oxidation experiments, which demonstrate that the selected NbTa-depletion HEC exhibits superior antioxidant performance compared to the equiatomic counterpart. The integrated computational-experimental approach presented in this work serves as a powerful framework to accelerate the discovery and development of oxidation-resistant HECs, paving the way for their expanded applications in demanding high-temperature, oxygen-rich environments.

Electronic, optical, phonon, and thermodynamic properties of bismuth oxyhalides for photocatalysis application using density functional theory

Bismuth oxyhalide (BiOX) represents a class of layered materials distinguished by unique physicochemical and optical characteristics. This study delivers an extensive investigation into the properties of BiOX crystals, employing first-principles calculations to analyze the electronic band structure, projected density of states (PDOS), Raman and infrared (IR) spectra, dielectric functions, alongside phonon and thermodynamic properties. The computed electronic band gaps BiOI, BiOBr, BiOCl, and BiOF crystals were determined to be 2.19 eV, 3.05 eV, 3.29 eV, and 3.43 eV, respectively. Furthermore, an analysis of the PDOS for each BiOX type indicates that the valence band maximum (VBM) primarily comprises dominant O 2p and halide X np states, while the conduction band minimum (CBM) predominantly features Bi 6p states. In addition, significant absorption edges for BiOI, BiOBr, BiOCl, and BiOF crystals, oriented along the [100] axis, were observed at wavelengths of 540 nm, 449 nm, 367 nm, and 320 nm, respectively. The Raman spectral analysis revealed a noticeable shift correlating with the increasing number of halogen atoms, with intensity enhancements observed at elevated temperatures. Phonon dispersion studies corroborated the geometric stability of the optimized structures of BiOX crystals. Thermodynamic evaluations suggested that BiOX materials exhibit qualities characteristic of hard materials at higher temperatures while displaying softer material attributes at lower temperatures. In summary, this research substantially enriches the current understanding of bismuth oxyhalides by detailing their structural, electronic, optical, phonon, and thermodynamic properties. The findings presented in this study provide a foundational basis for future advancements in photocatalytic applications and material development.

Observation of Enhanced Long-Range Ferromagnetic Order in B-Site Ordered Double Perovskite Oxide Cd2CrSbO6.

A B-site ordered double perovskite oxide Cd2CrSbO6 was synthesized under high-pressure and high-temperature conditions. The compound crystallizes to a monoclinic structure with a space group of P21/n. The charge configuration is confirmed to be that of Cd2+/Cr3+/Sb5+. The magnetic Cr3+ ions form a tetrahedral structural frustrated lattice, while a long-range ferromagnetic phase transition is found to occur at TC = 16.5 K arising from the superexchange interaction via the Cr-O-Cd-O-Cr pathway. Electrical transport measurements indicate that Cd2CrSbO6 is an insulator that can be described by the Mott 3D variable range hopping mechanism. First-principles calculations reproduce well the ferromagnetic and insulating ground state of Cd2CrSbO6 with an energy band gap of 1.55 eV. The intrinsic ferromagnetic insulating nature qualifies Cd2CrSbO6 as a promising candidate for possible spintronics applications.

Specifics of Al substitution into boron carbide: A DFT study

Boron carbide (B4C), known for its hardness and low density, is prone to local amorphization under high non-hydrostatic loads, limiting its applications. Aluminum doping is promising due to aluminum's atomic size, fitting into the B4C crystal lattice, particularly the intericosahedra chain, potentially reducing amorphization. This work uses first-principles calculations to study aluminum placement in B4C. We examine the potential for Al substitution in the icosahedron and intericosahedra chain, identifying possible locations. Results show that aluminum can't replace atoms in the icosahedron, but substituting one central atom in the intericosahedra chain with aluminum is energetically favorable and likely changes the chain configuration to an angular one. Additionally, aluminum can substitute one carbon in the (C-B-C) chain of B12(C-B-C) boron carbide. Comparative analysis suggests these configurations may coexist. Our study offers a theoretical model that can guide future experimental efforts and provides valuable insights into the structural specifics of aluminum-doped boron carbide.

Influences of Zr and V Addition on the Crystal Chemistry of θ-Al13Fe4 and the Grain Refinement of α-Al in an Al-4Fe Alloy Based on Experiment and First-Principle Calculations

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al13Fe4, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with more compact structures, such as α-Al15(Fe,Mn)3Si2. The addition of alloying elements is a crucial strategy for modifying the microstructure during the solidification process of aluminum alloys. This study investigates the effects of adding vanadium (V) and zirconium (Zr) on the morphology and crystal chemistry of θ-Al13Fe4 in an Al-4Fe alloy, employing a combination of experimental observations, first-principle calculations, and thermodynamic analysis. Our findings indicate that zirconium significantly refines both the primary θ-Al13Fe4 particles and the α-Al grains. Additionally, a small amount of vanadium can be incorporated into one of the Wyckoff 4i Al sites in θ-Al13Fe4, rather than occupying any Fe sites, under casting conditions, in addition to the formation of binary Al-V phases.

Computational screening of single-atom transition metals on boron-rich boron nitride nanosheets for efficient hydrogen evolution catalysis in all pH range.

Low-cost and high-efficiency catalysts are of crucial importance for the electrocatalytic hydrogen evolution reaction (HER). Two-dimensional (2D) boron nitride (B-N) compounds formed by the combination of boron and nitrogen atoms of group III and V elements are promising candidates for electrocatalytic HER due to their significant electronic properties. Hence, an electrocatalyst is computer-aided designed with isolated single atoms of 3d, 4d, and 5d transition metals supported on 2D B-N (B2N, B5N3, and B7N5) monolayers to fabricate single-atom catalysts (SACs) with an excellent HER performance. Moreover, pH modulations are considered to improve the HER activity theoretically based on first-principles calculation. Our results indicate that B-N compounds surface doping with transition metal atoms can effectively enhance the HER catalytic performance over a wide range of pH. Among all SACs studied, Co-, Ti-, V-, Nb-, Ru-, Tc-, Zr-, and Os-embedded B2N, Sc-, Cr-, Mn-, Ti-, and Y-embedded B5N3, and Sc- and Mn-embedded B7N5 have excellent catalytic activity under acidic conditions, while Mo-, Ir-, Re-, Ta-, and W-embedded B2N and Ti- and Fe-embedded B7N5 show high catalytic activity under alkaline conditions. Interestingly, Hf@B2N and V@B5N3 systems exhibit promising catalytic activity under acidic, neutral, and alkaline conditions. Our work offers cost-effective candidates with a wide pH range HER performance for exploring ideal electrocatalysts.

Designing C9N10 Anchored Single Mo Atom as an Efficient Electrocatalyst for Nitrogen Fixation.

Electrochemical nitrogen reduction reaction (NRR) is a promising route for realizing green and sustainable ammonia synthesis under ambient conditions. However, one of the major challenges of currently available Single-atom catalysts (SACs) is poor catalytic activity and low catalytic selectivity, which is far away from the requirements of industrial applications. Herein, first-principle calculations within the density functional theory were performed to evaluate the feasibility of a single Mo atom anchored on a g-C9N10 monolayer (Mo@g-C9N10) as NRR electrocatalysts. The results demonstrated that the gas phase N2 molecule can be sufficiently activated on Mo@g-C9N10, and N2 reduction dominantly occurs on the active Mo atom via the preferred enzymatic mechanism, with a low limiting potential of -0.48 V. In addition, Mo@g-C9N10 possesses a good prohibition ability for the competitive hydrogen evolution reaction. More impressively, good electronic conductivity and high electron transport efficiency endow Mo SACs with excellent activity for electrocatalytic N2 reduction. This theoretical research not only accelerates the development of NRR electrocatalysts but also increases our insights into optimizing the catalytic performance of SACs.

High density cobalt single atom catalysts for H2O2 electrosynthesis: A critical design of carbon nitride skeleton

Direct hydrogen peroxide (H2O2) electrosynthesis via the two-electron oxygen reduction reaction (ORR) provides aburgeoning alternative to the industrial anthraquinone process.In this work, based on first-principles calculations and a targeted structural search, we predicted a new two-dimensional (2D) carbon nitride monolayer, PH-CN, accompanied by high mechanical stability and adequate intrinsic pyrrolic N-rich network, such remarkable merits ensure its greatpotential as substrates. Herein, we demonstrate how the coordination environment regulates the electronic structure of the Co central atom and thus steers the ORR selectivity and activity using a series of control samples based on the most prevalent CoN4 moiety. As expected, the acquired P-CoN4 and PH-CoN4 show excellent H2O2electrosynthesis performance with low thermodynamic overpotential of 0.02 and 0.07 V, as well as extremely high Co loadings of 26.28 and 27.42 wt%, respectively. This work sheds light on how the carbon nitride skeleton affects catalytic activities on Co-N-C catalysts.

Hysteresis behavior and magnetocaloric effect in MnNiGa[formula omitted] full-Heusler alloy

In this manuscript, we studied the magnetic, magnetocaloric, and hysteresis properties of the MnNiGa2 full-Heusler alloy using mean-field theory and first-principles calculations. Initially, we employed the GGA+U method to investigate the structural characteristics of the alloy. Our findings indicated that the ferromagnetic state, with an optimal lattice parameter of 5.88 Å, was the most stable compared to the antiferromagnetic states. Additionally, the exchange interactions, defined as the Hamiltonian parameters of the studied system, were calculated and used in the mean-field approximation. The second-order transition at a Curie temperature of Tc = 373 K, previously revealed experimentally, has been confirmed. Furthermore, the alloy exhibited a relative cooling power (RCP) of 260.43 J/kg and a magnetocaloric effect of 10.34 J/kg.K at an applied magnetic field of 1.4 T. These results suggest that MnNiGa2 is a promising candidate for magnetic refrigeration applications.