Magnetic Moment Collapse-Driven Mott Transition in MnO

The metal-insulator transition in correlated electron systems, where electron states transform from itinerant to localized, has been one of the central themes of condensed matter physics for more than half a century. The persistence of this question has been a consequence both of the intricacy of the fundamental issues and the growing recognition of the complexities that arise in real materials, even when strong repulsive interactions play the primary role. The initial concept of Mott was based on the relative importance of kinetic hopping (measured by the bandwidth) and on-site repulsion of electrons. Real materials, however, have many additional degrees of freedom that, as is recently attracting note, give rise to a rich variety of scenarios for a ``Mott transition.'' Here we report results for the classic correlated insulator MnO which reproduce a simultaneous moment collapse, volume collapse, and metallization transition near the observed pressure, and identify the mechanism as collapse of the magnetic moment due to increase of crystal field splitting, rather than to variation in the bandwidth.Comment: 18 pages, 5 figur

Неэмпирическое исследование спин-переориентационного фазового перехода в PrCo₅₋ₓNiₓ (x = 0-5)

The series PrCo₅₋ₓNiₓ (x = 0-5) was investigated within the LDA+U+SO method taking into account strong correlations and spin-orbit coupling in Pr-4f, as well as in Ni(Co)-3d states. We give a detailed description of total energies, electronic structure and magnetic moments directions and values for all ions and concentrations considered. It was obtained that the system pass through a continuous spin transition from planar ab to the c axis directions of the Pr ion in agreement with experimentsСерия PrCo₅₋ₓNiₓ (x = 0-5) исследовалась в рамках метода LDA+U+SO с учетом сильных кор- реляций и спин-орбитальной связи в Pr-4f, а также Ni(Co)-3d электронных состояниях. При- водится детальное описание полных энергий, электронной структуры и направлений и величин магнитных моментов всех ионов для рассмотренных концентраций. Обнаружено, что в системе происходит непрерывный спиновый переход на ионе Pr из плоскостного направления ab в направ- ление вдоль оси c в согласии с экспериментам

Electronic Structure of Intermetallic Antiferromagnet GdNiGe

The electronic structure of the GdNiGe ternary intermetallic compound was investigated in this work. We carried out the spin-polarized DFT+U calculations of its band structure within generalized gradient approximation accounting for strong electronic correlations in the 4f-shell of gadolinium ions. The antiferromagnetic ordering was reproduced in the calculations, in agreement with experimental data. The calculated equilibrium volume is within 2% accuracy to the experimental crystal structure data, which demonstrates the reliability of the method chosen. The 4f-shell of Gd was demonstrated to substantially contribute to the spectral and magnetic properties of the GdNiGe compounds, whereas other ions were found nonmagnetic, in agreement with experimental data

Comparison of Band Structures of ErSb and ErNiSb Intermetallics from Ab Initio Calculations

RNiSb intermetallics are composed of R-rare earth, T-transition metals, and X-p elements. This family of compounds demonstrates many outstanding properties and phenomena perspectives in functional applications. The intermetallic compounds are crystalized in the cubic half-Heusler structure (space group F4¯3 m). Similar binary RSb compounds with the same crystal structure are topological semimetals with unusual Dirac-cone-like states observed in ARPES studies. In this work, the band structure and magnetic properties of ErSb and ErNiSb compounds are investigated in the framework of the DFT+U method comprising the density functional theory and correction for strong electron correlations in Er 4f shell. The calculated magnetic properties of both alloys obtained, to be solely caused by the magnetic moments of the Er ions, provide good agreement with the experimental data. ErSb has the band structure of a topological semimetal. A narrow energy gap was found in the band structure of ErNiSb, i.e., this alloy is an indirect gap semiconductor. The energy gap in ErNiSb was calculated to be 0.25 eV due to the minority spin projection. The band structure exhibits the presence of occupied bands, which can form a hole pocket near Γ in the L-Γ-X and K-Γ directions. In the band structure of ErSb, one can find the hole pockets near the same k-point along L-Γ-X, K-Γ and an electron pocket along Γ-X-W. These bands form topological features in ErSb, in particular, and cause a semimetallic state

Неэмпирическое исследование спин-переориентационного фазового перехода в PrCo₅₋ₓNiₓ (x = 0-5)

The series PrCo₅₋ₓNiₓ (x = 0-5) was investigated within the LDA+U+SO method taking into account strong correlations and spin-orbit coupling in Pr-4f, as well as in Ni(Co)-3d states. We give a detailed description of total energies, electronic structure and magnetic moments directions and values for all ions and concentrations considered. It was obtained that the system pass through a continuous spin transition from planar ab to the c axis directions of the Pr ion in agreement with experimentsСерия PrCo₅₋ₓNiₓ (x = 0-5) исследовалась в рамках метода LDA+U+SO с учетом сильных кор- реляций и спин-орбитальной связи в Pr-4f, а также Ni(Co)-3d электронных состояниях. При- водится детальное описание полных энергий, электронной структуры и направлений и величин магнитных моментов всех ионов для рассмотренных концентраций. Обнаружено, что в системе происходит непрерывный спиновый переход на ионе Pr из плоскостного направления ab в направ- ление вдоль оси c в согласии с экспериментам

Effect of manganese doping on the electronic structure and optical properties of Ce

In this paper we investigate the electronic structure and optical properties of the Ce2Fe17-xMnx (x = 0, 1, 2) intermetallic compounds and their change with the Mn-concentration growth within theoretical ab initio calculations. From these results we plot and compare experimental and theoretical optical conductivity utilizing interband transitions to interpret the experimental curve. To estimate the influence of manganese substitutions on the 3d sublattice, exchange Fe/Mn interaction parameters were computed and analysed. It was found that for the Mn substitutional impurity in the dumbbell positions the dominating ferromagnetic exchange interaction becomes the antiferromagnetic one favoring noncollinear magnetic ordering which was found in Ce2Fe17-xMnx at low temperatures

Electronic structure of DyRhSn and HoRhSn compounds: band calculations and optical study

In this paper experimentally measured optical properties of intermetallic ternary compounds DyRhSn and HoRhSn are reported together with the spin-polarized calculations of the electronic structure within DFT+U method, accounting for electronic correlation effects in the 4f shell of Dy and Ho. A number of spectral and electronic characteristics are determined. The performed calculations allow one to qualitatively interpret the energy dependencies of the interband optical conductivity extracted from experimental ellipsometry measurements