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Crystal structure and magnetic properties of Heusler alloys MnXNiSn (X = Mn, Fe, Co) are investigated using density functional theory and compared with experimental results. The parent alloy Mn2NiSn, which crystallizes in the inverse Heusler structure, is found to be ferrimagnetic, in agreement with previous experimental and theoretical work. The Fe and Co substitutions cause the alloys to assume a fairly well-ordered Y structure and enhance the magnetization substantially. We find that the strong nearest neighbour Mn-X exchange changes from antiferromagnetic (X = Mn) to ferromagnetic (X = Fe, Co), which explains and actually overestimates the experimental changes. A striking feature of the system is that Fe and Co have opposite effects on the Curie temperature Tc: they reduce and enhance Tc, respectively. We qualitatively explain this behaviour in terms of two-sublattice model based on the nearest-neighbour exchange. [ABSTRACT FROM AUTHOR]

Structural, electronic and magnetic properties of the Heusler alloy Mn2VIn have been investigated using the density functional theory and experimental techniques. Unlike many other Heusler compounds, Mn2VIn is not predicted to be half-metallic at the optimized lattice constant, but is highly spin polarized at a slightly lower lattice constant. It however exhibits ferrimagnetic coupling between the Mn and V sublattices, as expected of Mn-based Heuslers. We have, then, synthesized the compound by arc melting and studied magnetic properties that are of interest fundamentally and for technological applications. The structural properties were determined using X-ray diffraction, revealing the presence of cubic and tetragonal phases in the sample. The chemical composition was determined using energy-dispersive X-ray spectroscopy together with the scanning electron microscope, and the magnetic properties were investigated by superconducting quantum interference device magnetometry. The alloy exhibits superparamagnetic spin blocking with a blocking temperature TB of 40 K. [ABSTRACT FROM PUBLISHER]

Bulk alloys and thin films of Fe-substituted Ti3Co5B2 have been investigated by first-principle density-functional calculations. The series, which is of interest in the context of alnico magnetism and spin electronics, has been experimentally realized in nanostructures but not in the bulk. Our bulk calculations predict paramagnetism for Ti3Co5B2, Ti3Co4FeB2 and Ti3CoFe4B2, whereas Ti3Fe5B2 is predicted to be ferromagnetic. The thin films are all ferromagnetic, indicating that moment formation may be facilitated at nanostructural grain boundaries. One member of the thin-film series, namely Ti3CoFe4B2, is half-metallic and exhibits perpendicular easy-axis magnetic anisotropy. The half-metallicity reflects the hybridization of the Ti, Fe and Co 3d orbitals, which causes a band gap in minority spin channel, and the limited equilibrium solubility of Fe in bulk Ti3Co5B2 may be linked to the emerging half-metallicity due to Fe substitution. [ABSTRACT FROM AUTHOR]

We report the fabrication of a rare-earth-free permanent-magnet material Co3Si in the form of nanoparticles and investigate its magnetic properties by experiments and density-functional theory (DFT). The DFT calculations show that bulk Co3Si has an easy-plane anisotropy with a high K1 ≈ 64 Merg/cm3 (-6.4 MJ/m3) and magnetic polarization of 9.2 kG (0.92 T). In spite of having a negative anisotropy that generally leads to negligibly low coercivities in bulk crystals, Co3Si nanoparticles exhibit high coercivities (17.4 kOe at 10K and 4.3 kOe at 300 K). This result is a consequence of the unique nanostructure made possible by an effective easy-axis alignment in the cluster-deposition method and explained using micromagnetic analysis as a nanoscale phenomenon involving quantum-mechanical exchange interactions. [ABSTRACT FROM AUTHOR]

The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX2; X=S, Se, and Te) are investigated using densityfunctional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX2 monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

The influence of substrate strain on the magnetic properties of Co–Pt multilayers is investigated by density functional theory (DFT) and model calculations. The lattice parameters for strained Co–Pt multilayers, which are needed as an input for first-principle calculations, are determined by a hybrid approach where DFT is used to determine the lattice constants and atomic positions of the free multilayer, and the effect of the strained substrate is treated continuum mechanically. The lowest order anisotropy constants have been calculated for unstrained and strained hcp Co2Pt4(111) and fcc Co1Pt5(111) multilayers on LiNbO3, and in the strained case, the anisotropy is nonunixial with nonzero anisotropy constant \(K_{1}\) and \(K_{1}\) ’. By involving both multilayer and substrate mechanical properties, our calculations go beyond the usually considered magnetoelastic anisotropy mechanisms. [ABSTRACT FROM AUTHOR]

Limitation in the synthesis of single-crystal has restricted the complete understanding of the magnetoelectric properties of bulk ε-Fe 2 O 3. In order to understand the electric polarization of bulk ε-Fe 2 O 3 , we have employed a first-principles Berry-phase method and the density functional perturbation theory to calculate the spontaneous electric polarization and Born effective charges (BECs) of ε-Fe 2 O 3. The polarization quanta of the ferroelectric bulk ε-Fe 2 O 3 and its polarization lattice are also reported. The polarization switching through a paraelectric transition phase of a low barrier is found to be favorable. The polarization and BECs calculated by both methods are in good agreement. [ABSTRACT FROM AUTHOR]

Highlights: [•] An electric field enhances the magnetization of organometallic vanadium–benzene nanowires. [•] Density-functional theory predicts changes much bigger than in metallic systems. [•] The electric field yields a reorientation of the easy magnetization axis. [Copyright &y& Elsevier]

Bulk alloys and thin films of Fe-substituted Ti3Co5B2 have been investigated by first-principle density-functional calculations. The series, which is of interest in the context of alnico magnetism and spin electronics, has been experimentally realized in nanostructures but not in the bulk. Our bulk calculations predict paramagnetism for Ti3Co5B2, Ti3Co4FeB2 and Ti3CoFe4B2, whereas Ti3Fe5B2 is predicted to be ferromagnetic. The thin films are all ferromagnetic, indicating that moment formation may be facilitated at nanostructural grain boundaries. One member of the thin-film series, namely Ti3CoFe4B2, is half-metallic and exhibits perpendicular easy-axis magnetic anisotropy. The half-metallicity reflects the hybridization of the Ti, Fe and Co 3d orbitals, which causes a band gap in minority spin channel, and the limited equilibrium solubility of Fe in bulk Ti3Co5B2 may be linked to the emerging half-metallicity due to Fe substitution. [ABSTRACT FROM AUTHOR]

The nanoscale structural, compositional,and magnetic propertiesare examined for annealed MnAu nanoclusters. The MnAu clusters orderinto the L10structure, and monotonicsize-dependences develop for the composition and lattice parameters,which are well reproduced by our density functional theory calculations.Simultaneously, Mn diffusion forms 5 Å nanoshells on larger clustersinducing significant magnetization in an otherwise antiferromagneticsystem. The differing atomic mobilities yield new cluster nanostructuresthat can be employed generally to create novel physical properties. [ABSTRACT FROM AUTHOR]