Magnetic Moments Of Mn Atoms Research Articles

First-principles calculations of the electronic, optical properties and quantum capacitance of Mn doped Sc2CO2 monolayer under biaxial strain

The electronic structures and quantum capacitance of Mn atom doped Sc2CO2 under biaxial strain are investigated by first-principles calculations. The results indicate that pristine Sc2CO2 monolayer is nonmagnetic, while Mn doping makes the system have the magnetic character, which is mainly from Mn and C atoms neighboring to Mn atom. The total magnetic moment under strain ranges from 2.16 μB to 2.69 μB. The local magnetic moment of Mn atom under strains ranges from 2.59 μB to 4.33 μB, and the variation in local magnetic moment has the largest value of 1.84 μB. Spin-up band structures under strain exhibit the characteristic of the indirect semiconductor, and have the largest band gap of 0.3 eV at −2 % strain. The spin-down band structures under strain show the character of direct semiconductor and the largest band gap is 1.83 eV at 2 % strain. Sc2CO2-Mn under strains except +5 % are suitable for cathode material, while Sc2CO2-Mn with +5 % strain changes to cathode material in ionic/organic system. Effective mass, work function, and optical properties are further explored.

Correlation between Local Structure and Reaction Mechanism in Disordered Rock-Salt-Type Lithium–Manganese Oxides

First-principles (FP) calculations of disordered rock-salt-type lithium–manganese oxides were performed by assuming a quasi-random structure model with the composition of Li16Mn16O32. The effects of randomness in the crystal structure and the changes in local atomic configurations during the Li extraction process on electronic structures, phase stability, and electrochemical properties were investigated by the FP calculations. The calculations indicate that the randomness of local atomic configurations, which originates from the disordered structure, makes it possible for Mn and O sites to take on a variety of electronic states. Analyses of densities of states, magnetic moments of Mn atoms, and Bader charges indicate the possibility that not only Mn but also oxygen atoms contribute to the redox reaction. The migration of Li and Mn is found to appear from octahedral to tetrahedral sites at a high state of charge. The FP calculations suggest that the change in local atomic configurations and electronic structures causes the transition in voltage profiles from sloping to 3 V plateau shape as the cycle progresses, which is characteristic of spinel-related positive electrode materials.

Electronic properties of the Mn<sub>3</sub>Z (Z = Ga, Ge) alloys: first-principles studies

The structural and electronic properties of Mn3Z alloys (Z = Ga, Ge) are studied ab initio. It is shown that in the cubic and tetragonal phases, the configuration with antiparallel orientation of magnetic moments of Mn atoms on different sublattices is energetically favorable. Calculations of the electronic densities of states show that the spin polarization of the tetragonal phase is about 60%. The results obtained are in good agreement with the experimental data.

Origin of the type-II Weyl state in topological antiferromagnetic YbMnBi2

Recently, the topological nature of an antiferromagnet YbMnBi2 has been controversial. YbMnBi2 is regarded as a candidate of Type-II Weyl semimetals with magnetic moments of Mn atoms canting about 10{\deg} in some studies but as a Dirac semimetal without canting in others. By means of systematical density functional theory calculations, we show the perfect YbMnBi2 bulk has a collinear antiferromagnetic ordering and, naturally, it is a Dirac semimetal. Considering the vital role of magnetic moment canting in generating the Type-II Weyl state, we artificially cant the magnetic moments of Mn atoms and find that YbMnBi2 enters into the Type-II Weyl state from about 2{\deg}. Inspired by this and taking into account the possible defects in experiments, we suggest that Bi vacancies in Mn-Bi-Mn bonds, which produce sizable Dzyaloshinskii-Moriya interactions and thereby cant the magnetic moments of Mn atoms, can tune the topological nature of YbMnBi2 from Dirac semimetals to Type-II Weyl semimetals. Our work unveils the possible underlying mechanism for the Type-II Weyl state in YbMnBi2, providing insights into the Weyl state in other magnetic topological materials.

Strain-dependent magnetism and anomalous Hall effect in noncollinear antiferromagnetic Mn3Pt films

The exploration of Berry curvature physics and the related non-trivial magnetic transport of two-dimensional kagome spin-lattice structure of Mn atoms in noncollinear antiferromagnetic materials, has received widespread attention in recent years. Current research is mainly focused on the hexagonal chiral antiferromagnets such as Mn3Sn. However, there are few researches about face-centered cubic (fcc) noncollinear antiferromagnetism. In this work, the influence of strain on the magnetic properties and the anomalous Hall effect (AHE) of the fcc noncollinear antiferromagnetic Mn3Pt films were systematically explored. The results showed that the ferromagnetic signal derived from the tilt of the magnetic moment of Mn atoms in the kagome structures, as well as the anomalous Hall resistance originating from the non-zero Berry curvature, had comparable response tendency to the strain, differing from hexagonal chiral antiferromagnets. An anomalous Hall conductivity exceeding 100 (Ω cm)−1 was obtained by tuning the film thickness of Mn3Pt. In addition, the relationship among the Berry phase, magnetic properties, and AHE in Mn3Pt was further verified by regulating the crystal growth orientation. The results established Mn3Pt as a promising candidate for its integration with room-temperature antiferromagnetic spintronics.

Structural and magnetic effects of Mn addition on CoB amorphous alloy by first principle simulation

First-principle molecular dynamics is employed to study the geometrical structure, electronic structure, and magnetic properties of Co80-xMnxB20 (x = 0, 2, 4, 6, 8, 10, 12 at.%) amorphous alloys. Results demonstrate that Mn atom locates at substituted positions of Co atoms, and cage structure with Mn as a center is mainly a twisted Icosahedral structure. Mn or Co atoms tend to lose electrons, and B atoms tend to gain electrons. The addition of Mn atoms increases the splitting of p band of B atoms. Variation of magnetic moment increases and then decreases with the increase of Mn content. Simulation results are in good agreement with experiments. Magnetic moment of Mn atoms in amorphous alloy exhibits ferromagnetic arrangement when x > 6 at.%. However, when x > 6 at.%, some antiferromagnetic arranged Mn atoms appear, and there is a competition between ferromagnetism and antiferromagnetism in the alloy, which makes magnetic moment of the amorphous alloy gradually decrease.

Ferrimagnetic–ferromagnetic phase transition in Mn4N films favored by non-magnetic In doping

The ferrimagnet Mn4N forms a family of compounds useful in spintronics. In a compound comprising non-magnetic and magnetic elements, one basically expects the compound to become ferromagnetic when the proportion of the magnetic element increases. Conversely, one does not expect ferromagnetism when the proportion of the non-magnetic element increases. Surprisingly, Mn4N becomes ferromagnetic at room temperature when the Mn content is decreased by the addition of In atoms, a non-magnetic element. X-ray magnetic circular dichroism measurement reveals that the magnetic moment of Mn atoms at face-centered sites, Mn(II), reverses between x= 0.15 and 0.27 and aligns parallel to that of Mn atoms at corner sites, Mn(I), at x = 0.27 and 0.41. The sign of the anomalous Hall resistivity also changes between x = 0.15 and 0.27 in accordance with the reversal of the magnetic moment of the Mn(II) atoms. These results can be interpreted using first-principles calculations, showing that the magnetic moment of Mn(II) sites which are the nearest neighbors to the In atom align to that of Mn(I) sites.

Cesium manganese chloride: Stable lead-free perovskite from bulk to single layer

Motivated by the recent advances in perovskite-based solar cells, here we investigate stability, electronic properties and vibrational characteristics of lead-free perovskite, CsMnCl3, and its low dimensional forms by means of first-principles calculations. Structural optimizations reveal that, regardless of whether it is bulk or ultra-thin single layer cubic perovskite structure, CsMnCl3 crystal exhibit robust antiferromagnetism in its ground state due to oppositely aligned magnetic moments of Mn atoms. In addition to total energy calculations, phonon band dispersions indicate that CsMnCl3 structure sustains its dynamical stability down to its thinnest single layer crystal structures. The calculated Raman spectrums state that while the first-order Raman scattering is forbidden for bulk CsMnCl3 due to the cubic symmetry; dimensional-reduction-driven symmetry breaking leads to emergence of experimentally-observable distinctive Raman active modes in bilayer and single-layer crystal structures. Moreover, the electronic band dispersions reveal that from its bulk to ultra-thin single layer structures CsMnCl3 crystals are robust antiferromagnetic insulators. Multiple valid features like controllable dimensionality, robust antiferromagnetism and wide electronic band gap make cubic CsMnCl3 crystal as a potential candidate for nano-scale optoelectronic applications.

Ferromagnetic exchange mechanism and martensitic transformation of Heusler alloy based on d-band center theory

In order to investigate the antiferromagnetic coupling of Co and Mn atoms in Cu2−xCoxMn1+yAl1−y, a Heusler alloy, under Mn rich condition, our basic research objects are Cu2MnAl with only one kind of magnetic atoms and Co2MnAl which remain ferromagnetic in Mn rich conditions. After a large number of calculations, we found that because the Co atom is higher than the d-band center of Cu atom, then the anti-bonding state of Mn atom is pushed above Fermi level, thus changing the d-orbital electron arrangement of Mn atom, making the original antiferromagnetic Mn atom become ferromagnetic. Based on this theory, a method of applying stress to the alloy to adjust the lattice size to change the magnetic moment of Mn atom is proposed to achieve the same effect as doping special atoms. In addition, it was also inferred that the ferromagnetism of the parent phase and the ferromagnetism of the martensite phase are closely related to the d-band center caused by the change of lattice size.

Electronic States and Magnetic Response of MnBi2Te4 by Scanning Tunneling Microscopy and Spectroscopy.

Exotic quantum phenomena have been demonstrated in recently discovered intrinsic magnetic topological insulator MnBi2Te4. At its two-dimensional limit, the quantum anomalous Hall effect and axion insulator state were observed in odd and even layers of MnBi2Te4, respectively. Here, we employ low-temperature scanning tunneling microscopy to study the electronic properties of MnBi2Te4. The quasiparticle interference patterns indicate that the electronic structures on the topmost layer of MnBi2Te4 are different from those of the expected out-of-plane A-type antiferromagnetic phase. The topological surface states may be embedded in deeper layers beneath the topmost surface. Such novel electronic structure is presumably related to the modification of crystalline structure during sample cleaving and reorientation of the magnetic moment of Mn atoms near the surface. Mn dopants substituted at the Bi site on the second atomic layer are observed. The electronic structures fluctuate at atomic scale on the surface, which can affect the magnetism of MnBi2Te4.

Investigation of Full-Heusler compound Mn2MgGe for magnetism, spintronics and thermoelectric applications: DFT study

First principle method based Density functional theory calculations are used to investigate electronic, magnetic, thermoelectric and lattice-dynamical properties of Full-Heusler compound Mn2MgGe. We considered the energetic, thermodynamical and lattice-dynamical stability criteria for Mn2MgGe by evaluating the total energy, formation energy, and phonon density of states respectively, which thereby suggest that the synthesis of Full-Heusler compound Mn2MgGe is possible. Half metallic spin-polarized nature from electronic band structure and total magnetic moment (2μB) of Hg2CuTi type structure of Mn2MgGe potentially facilitate its spintronics applications. The results of electronic structure and magnetism predicts that Hg2CuTi type structure of Mn2MgGe is an indirect band gap semiconductor with half-metallic ferrimagnetic behaviour. Antiparallel and equal magnetic moment of Mn atoms cancel out the magnetization in Cu2MnAl type structure of Mn2MgGe, making its total magnetic moment 0 μB/cell. The electronic and magnetic properties for Cu2MnAl type structure of Mn2MgGe has not been previously reported. Positive and negative value of Seebeck coefficient for spin up and spin down channel indicate the presence of P-type and N-type charge carriers in the compound. Mn2MgGe exhibits high Seebeck coefficient −38 μV/K and 180 μV/K in spin-up and spin-down channel at room temperature (300 K) along with huge power factor of 4.23×1011 w/mK2s at 600 K, predicting Mn2MgGe as a potential candidate for thermoelectric applications.

Magnetic moment of Mn in disordered Pd2MnGe Heusler alloy as studied by CPA and supercell modelling

Abstract The neutron-scattering measurements and the observation of hyperfine interaction of nuclear moments in Pd2MnGe alloy have prompted a study of disorder in this compound by the density functional theory methods. Two approaches: the coherent-potential approximation (CPA) and supercell modelling were used to gain microscopic insight into the electronic and magnetic properties of disordered Pd2MnGe. The influence of disorder between Pd and Mn sublattices in Pd2MnGe on the magnetic moment of Mn atoms is discussed. The presented CPA studies have shown that the small disorder in Pd2MnGe (between the Pd-Mn sublattices of the L21 structure) does not well describe the experimental evidence of antiparallel alignment of magnetic moment of Mn at positions (A,C) and B positions. However, the appearance of antiparallel moment of Mn at positions A and B was predicted for the Pd2MnGe in the frames of 128-atoms supercell calculations. The generalized gradient approximation (GGA) has been the main basis for the presented supercell first-principles electronic structure calculations. The magnetic moment of Mn(A,C) is found to be small and negative value of −0.177 µB. The values of magnetic moment of Mn(B) are between 3.6 µB and 3.72 µB. The results obtained for the supercell calculations are consistent with available experiments in the literature. The results of presented calculations in the supercell approach have shown that the disordered Pd2MnGe can be predicted as a mixture of several supercells.

Theory of Mn-Based High-Magnetization Alloys

The realization of the magnetic moment of Mn atoms in ferromagnetic alloys is investigated theoretically. This paper is partly motivated by the recent discovery of high-magnetization Fe–Co–Mn thin films by Snow et al. , who reported moments of up to 3.25 $\mu _{\text {B}}$ per atom. Structural and strain effects are discussed with particular emphasis on the distinction between tetragonal martensitic lattice distortions and Bain transitions in body-centered cubic, CsCl, and Heusler alloys. It is outlined how these lattice distortions affect the electronic structure of the alloys, and ab initio calculations are used to determine the net moment of cubic Fe6Co63Mn31. The calculated moment, $2.90~\mu _{\text {B}}$ per atom, is reasonably close to the experimental value.

Phase Stabilities and Magnetic Properties of Mn-Deficient and Ge-Substituted Mn3Ga With D022Structure

We have investigated phase stabilities and magnetic properties of the tetragonal D022 phase in Mn-deficient Mn3– x Ga and Ge-substituted Mn3Ga1– y Ge y . A transition from the D022 to L10 phase is observed in the composition range of $x = 0.5$ –0.8 in Mn3– x Ga. On the other hand, the D022 phase is confirmed in the overall composition of Mn3Ga1– y Ge y . The thermal stability of the D022 phase strongly depends on the Ge content compared with the Mn deficiency. Magnetization of Mn3– x Ga is increased by introducing the Mn deficiency, whereas that of Mn3Ga1– y Ge y decreases with increasing Ge content despite a constant number of Mn atoms. This result suggests that the magnitude of magnetic moment of Mn atom in Mn3Ga1– y Ge y is influenced by variations of valence electron and structural properties caused by the Ge substitution.

Ab initio investigation of supported Au–Mn nanowires

We present an ab initio study of surface supported Au–Mn nanowires. Three different substrates are discussed: Cu(110), stepped Cu(111) and Si(001) surface. The emergence of stable antiferromagnetic (AFM) solutions in Au–Mn nanowires was found in all three cases. We found the nonzero magnetic moments of Mn atoms, however, the bulk of manganese is paramagnetic. The critical temperature of the Au–Mn wires is calculated by means of kinetic Monte Carlo simulation. The strong size-effect of the critical temperature is demonstrated.

Half-metallic fully compensated ferrimagnetism in C1b-type half Heusler compounds Mn2Si1−xGex

First-principles electronic structure calculations have been performed for the 18-valence electrons compounds Mn2Si1−xGex(x=0, 0.25, 0.5, 0.75, 1). The results suggest that Mn2Si1−xGex compounds in C1b structure are half-metallic fully compensated ferrimagnets. Furthermore, the size of the half-metallic band gap, the position of the Fermi level, and the magnetic moment of Mn atoms can be manipulated by changing x from 0 to 1 without destroying the half-metallic fully compensated ferrimagnetic property.

The Effect of Phase Decomposition on Magnetic Structure of Cu0.4Mn0.3Ni0.3Alloy

The purpose of present investigation was to study the e ects of phase decomposition of the Cu0.4Mn0.3Ni0.3 alloy on its magnetic ordering. The single-crystal sample was examined by elastic neutron scattering before and after ve subsequent annealing runs. The results indicate that in small fraction of the quenched sample volume there are two types of antiferromagnetic order: one of them AF1 of the long range, the other one of the short range. Ageing induces phase decomposition which yields disappearance of AF1 long range order and increase of the volume of new ordered phase. The results of the investigations of the aged sample indicate that regions of new tetragonal phase exhibit antiferromagnetic ordering with magnetic moments of Mn atoms arranged as in the pure compound MnNi but with unequal domain distribution. The intensity of magnetic component of super-structure re ections increases with the duration of ageing at lower rate than component due to atomic order.

Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands

Abstract By means of the density functional theory combined with non-equilibrium Green's function method, ballistic transport properties of one-dimensional noncollinear magnetic monatomic chains were investigated using the single-atomic Mn chains as a model system. Fano resonances are found to exist in the monatomic Mn chains with spin-spiral structure. Furthermore, in the monatomic Mn chains with magnetic soliton lattice, Fano resonances are enhanced and cause the conductance splitting in the transmission spectra. The Fano resonances in the noncollinear magnetic single-atomic Mn chains are arising from the coupling of the localized d -states and the extended states of the quantum channels. By constructing a theoretical model and calculating its conductance, it is found that the phenomena of Fano resonances and the accompanying conductance splitting exist universally in the superlattice of one-dimensional noncollinear magnetic barriers, due to the interference of the incident waves and reflected waves by the interfaces between the neighboring barriers. Moreover, the band structures of the ferromagnetic and spin-spiral monatomic Mn chains exhibit a strong dependence on the spatial arrangement of the magnetic moments of Mn atoms when spin–orbit coupling is considered.

Superparamagnetism, magnetoresistance and anomalous Hall effect in amorphous MnxSi1−x semiconductor films

A systematic study focusing on the magnetic and transport properties of Mn0.48Si0.52 semiconductor films is performed. The Mn0.48Si0.52 films show superparamagnetism above 17K. The temperature dependence of the electrical transport reveals that electron–electron and electron–phonon interactions dominate the conductivity of weakly localized carriers. Very small negative magnetoresistance suggests that spin-dependent scattering between conductive carriers and local magnetic moments of Mn atoms is rather weak. On the contrary, the anomalous Hall effect due to the skew scattering is observed in the whole temperature range, indicating the spin–orbit coupling of the conducting carriers is significantly strong.

Density functional study of manganese atom adsorption on hydrogen-terminated armchair boron nitride nanoribbons

In this paper, we have investigated stable structural, electric and magnetic properties of manganese (Mn) atom adsorption on armchair hydrogen edge-terminated boron nitride nanoribbon (A-BNNRs) using first principles method based on density-functional theory with the generalized gradient approximation. Calculation shows that Mn atom situated on the ribbons of A-BNNRs is the most stable configuration, where the bonding is more pronounced. The projected density of states (PDOS) of the favored configuration has also been computed. It has been found that the covalent bonding of boron (B), nitrogen (N) and Mn is mainly contributed by s, d like-orbitals of Mn and partially occupied by the 2p like-orbital of N. The difference in energy between the inner and the edge adsorption sites of A-BNNRs shows that Mn atoms prefer to concentrate at the edge sites. The electronic structures of the various configurations are wide, narrow-gap semiconducting and half-metallic, and the magnetic moment of Mn atoms are well preserved in all considered configurations. This has shown that the boron nitride (BN) sheet covered with Mn atoms demonstrates additional information on its usefulness in future spintronics, molecular magnet and nanoelectronics devices.