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α″–Fe16N2 has been investigated as one of promising candidates for environment-friendly magnets. While giant saturation magnetization has previously been experimentally observed in α″–Fe16N2, its magnetic anisotropy and structural stability leave room for improvement. Recent theoretical studies have considered alloying Fe16N2 with various elements to improve the magnetic properties and/or stability against decomposition. However, estimates of stability in particular are typically restricted to simple ground-state-energy comparisons, i.e. effectively taken at 0 K. For a more practical measure of stability, we therefore extend ground-state energies, obtained with the plane-wave density-functional theory code Quantum ESPRESSO, with appropriate empirical and/or statistical corrections to obtain free energies at arbitrary temperature. We then compare the stability of Fe16N2 against the neighboring phases in the Fe-N binary system, to estimate the range of temperatures at which it is stable. We compare against experimental observations of the Fe-N phase diagram. [ABSTRACT FROM AUTHOR]

Contrary to topological insulators, topological semimetals possess a nontrivial chiral anomaly that leads to negative magnetoresistance and are hosts to both conductive bulk states and topological surface states with intriguing transport properties for spintronics. Here, we fabricate highly-ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering technology. Systematic angular dependence (both in-plane and out-of-plane) study of magnetoresistance presents surprisingly robust quadratic and linear negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x, respectively. We attribute the anomalous negative longitudinal magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or the formation of tunable Weyl semimetal phases through symmetry breaking processes, such as magnetic-atom doping, as confirmed by first-principles calculations. Furthermore, Pt3Sn and Pt3SnxFe1-x show the promising performance for facilitating the development of advanced spin-orbit torque devices. These results extend our understanding of chiral anomaly of topological semimetals and can pave the way for exploring novel topological materials for spintronic devices. Negative longitudinal magnetoresistance refers to a decrease in resistance with the external magnetic field when the field direction is applied parallel to the current direction. It is considered an experimental signature of topological semimetals. Here, Zhang et al find clear and robust quadratic and linear negative longitudinal magnetoresistance in Pt3Sn and Pt3SnxFe1-x films. [ABSTRACT FROM AUTHOR]

The ordered iron nitride phase α″–Fe16N2 has been a potential candidate for rare-earth free magnets with giant saturation magnetization, but first-principles electronic-structure calculations have struggled to reproduce recent observations of high magnetic moment, while calculations of magnetocrystalline anisotropy (MCA) vary significantly. Within the framework of density-functional theory (DFT), a common extension to the usual generalized-gradient approximation (GGA) exchange-correlation (XC) functional is the inclusion of Hubbard parameters U (,J) as GGA + U. A number of previous papers have applied this method to Fe16N2, each with their own choice of Hubbard parameters. The plane-wave DFT code Quantum ESPRESSO was employed to more comprehensively study the effect of the value of Hubbard parameters U and J on the system, particularly with respect to its magnetic properties. Various approaches for setting U and J were compared, including self-consistent calculations via the linear-response method. [ABSTRACT FROM AUTHOR]

The ordered iron nitride phase α″–Fe16N2 has been a potential candidate for rare-earth free magnets with giant saturation magnetization, but first-principles electronic-structure calculations have struggled to reproduce recent observations of high magnetic moment, while calculations of magnetocrystalline anisotropy (MCA) vary significantly. Within the framework of density-functional theory (DFT), a common extension to the usual generalized-gradient approximation (GGA) exchange-correlation (XC) functional is the inclusion of Hubbard parameters U (,J) as GGA + U. A number of previous papers have applied this method to Fe16N2, each with their own choice of Hubbard parameters. The plane-wave DFT code Quantum ESPRESSO was employed to more comprehensively study the effect of the value of Hubbard parameters U and J on the system, particularly with respect to its magnetic properties. Various approaches for setting U and J were compared, including self-consistent calculations via the linear-response method. [ABSTRACT FROM AUTHOR]

While giant saturation magnetization has been observed in α″–Fe16N2, its magnetic anisotropy and structural stability leave room for improvement. Several recent studies have investigated the effect of substitution to improve its magnetic properties and/or its stability; among these, substitution of Fe with V or Cu has shown promise. We thus compare the magnetic properties of such alloys in some more detail using first-principles electronic-structure calculations: The magnetocrystalline anisotropy (MCA) energies of ordered Fe16–nVnN2 and Fe16–nCunN2 alloys (n=1, 2), as well as the co-substituted alloy Fe14VCuN2, are obtained within the plane-wave density-functional theory (DFT) code Quantum ESPRESSO. [ABSTRACT FROM AUTHOR]

While giant saturation magnetization has been observed in α″–Fe16N2, its magnetic anisotropy and structural stability leave room for improvement. Several recent studies have investigated the effect of substitution to improve its magnetic properties and/or its stability; among these, substitution of Fe with V or Cu has shown promise. We thus compare the magnetic properties of such alloys in some more detail using first-principles electronic-structure calculations: The magnetocrystalline anisotropy (MCA) energies of ordered Fe16–nVnN2 and Fe16–nCunN2 alloys (n=1, 2), as well as the co-substituted alloy Fe14VCuN2, are obtained within the plane-wave density-functional theory (DFT) code Quantum ESPRESSO. [ABSTRACT FROM AUTHOR]