Insights into formation and stability of τ-MnAlZx (Z = C and B)

Fang, Hailiang; Cedervall, Johan; Martínez-Casado, Francisco J.; Matěj, Zdeněk; Bednarčı́k, J.; Ångström, Jonas; Berastegui, P.; Sahlberg, Martin

doi:10.1016/j.jallcom.2016.09.047

Cited by 40 publications

(12 citation statements)

References 28 publications

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“…Therefore, the crossing points will form a new structure of nodal lines, i.e. "nodal-cylinder" along k z direction in the whole BZ, which is different from other simple nodal-line semimetals, 21,22,25,53,54 nodal-chain metals, 29 nodal-net semimetals, 24, 28 nodal-link semimetals, 17,55,56 and nodal-knot semimetals. 57 As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Prediction of two-dimensional nodal-line semimetals in a carbon nitride covalent network

et al. 2018

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Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C 3 N 4 , nitrogenated holey grahpene C 2 N, polyaniline C 3 N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C 9 N 4 stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C 9 N 4 is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C 9 N 4 forms a closed ring centered at  point, which originates from the p z orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome 2 and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in nature induced by the chemical potential difference of C and N, as validated by a single orbital tight-binding model, rather than protected by crystal in-plane mirror symmetry or band topology. Interestingly, a new structure of nodal line, i.e., nodal-cylinder, is found in momentum space for AA-stacking C 9 N 4 . Our results imply possible functionalization for a novel metal-free C-N covalent network with interesting semimetallic properties.

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Section: Resultsmentioning

confidence: 99%

Prediction of two-dimensional nodal-line semimetals in a carbon nitride covalent network

et al. 2018

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“…Recently, topological phases have been significantly extended from gapped topological insulators [1,2], such as quantum spin Hall states [3][4][5], quantum anomalous Hall states [6][7][8][9], three-dimensional topological insulators [10][11][12] and topological superconductors [13][14][15][16][17], to gapless topological semimetals, such as Weyl semimetals , Dirac semimetals [41][42][43][44][45][46][47][48][49][50][51][52][53], and nodal-line semimetals [54][55][56][57][58][59][60][61][62]. Unlike topological insulators, topological semimetals have stable bulk-band-touching points or closed lines in the Brillouin zone, leading to the emergence of lowenergy quasiparticles, known as Weyl fermions, Dirac fermions, and nodal-line fermions, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Both Dirac and Weyl semimetals manifest topologically protected surface Fermi arcs and exotic transport properties originating from the chiral anomaly, such as negative magnetoresistance and chiral magnetic effects [63][64][65][66][67][68][69][70][71][72][73]. Dirac semimetals and nodal-line semimetals require special symmetries, such as, time-reversal symmetry (TRS), inversion symmetry (IS), and crystal symmetries [41,47,51,57,58,74], while Weyl semimetals can be in a stable existence without any symmetries.…”

Section: Introductionmentioning

confidence: 99%

Engineering topological phases in the Luttinger semimetal α -Sn

et al. 2018

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α-Sn is well known as a typical Luttinger semimetal with a quadratic band touching at the Γ point. Based on the effective k·p analysis as well as first-principles calculations, we demonstrate that multiple topological phases with a rich diagram, including topological insulator, Dirac semimetal, and Weyl semimetal phases, can be induced and engineered in α-Sn by external strains, magnetic fields, and circularly polarized light (CPL). Intriguingly, not only the conventional type-I Weyl nodes, but also type-II Weyl nodes and double-Weyl nodes can be generated directly from the quadratic semimetal by applying a magnetic field or CPL. Our results apply equally well to other Luttinger semimetals with similar crystal and electronic structures, and thus open an avenue for realizing and engineering multiple topological phases on a versatile platform.

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“…Addition of carbon at the octahedral interstitial sites (½, ½, 0) have proven to be an effective way of stabilizing the tetragonal structure with an elongation along the c axis 11 , 12 . Previous studies by us have also shown the importance of carbon doping on the stability of the τ-phase 13 , 14 and in the present study only carbon doped samples were used. Carbon furthermore has an effect of increasing the saturation magnetization but reduces the Curie temperature and the anisotropy 12 , 15 .…”

Section: Introductionmentioning

confidence: 64%

“…The second approach is through ball/surfactant milling of the gas atomized or induction/arc melted sample followed by magnetic field compaction 23 . The former method is too expensive and the latter one produces flakes with random crystallographic orientation due to the large ductility of MnAl, thus impeding proper orientation of the grains in a magnetic field 13 , 23 – 25 . Consequently, the preparation of powders consisting of regularly shaped single grain particles would be critically important for the success of a high performance anisotropic permanent magnet material 26 .…”

Section: Introductionmentioning

confidence: 99%

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

Fang

Cedervall

Hedlund

et al. 2018

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The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a flash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4 hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the flash heated samples display high saturation magnetization as well as increased coercivity.

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Insights into formation and stability of τ-MnAlZx (Z = C and B)

Cited by 40 publications

References 28 publications

Prediction of two-dimensional nodal-line semimetals in a carbon nitride covalent network

Prediction of two-dimensional nodal-line semimetals in a carbon nitride covalent network

Engineering topological phases in the Luttinger semimetal α -Sn

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

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