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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Phonon modes and Raman signatures of MnBi 2n Te 3n+1 (n=1,2,3,4) magnetic topological heterostructures

An intrinsic antiferromagnetic topological insulator MnBi 2 Te 4 arises when intercalating a Mn-Te bilayer chain in a topological insulator, Bi 2 Te 3 . We present observations on the inter- and intralayer phonon modes of the generalized MnBi 2n Te 3n+1 (n=1,2,3,4) family using cryogenic low-frequency Raman spectroscopy with various polarization configurations. Two peaks at 66 and 112 cm –1 show abnormal perturbation in Raman linewidths below magnetic transition temperature due to spin-phonon coupling. In MnBi 4 Te 7 , B i2 Te 3 layers induce Davydov splitting of the A1g mode around 137 cm –1 at 5 K. The out-of-plane interlayer force constant estimated using the linear chain model was (3.98±0.14)×10 19 N/m 3 , three times weaker than that of Bi 2 Te 3 . Adding more Bi 2 Te 3 layers, such as MnBi 6 Te 10 and MnBi 8 Te 13 , makes Bi 2 Te 3 properties more dominant than magnetic properties. Our work experimentally and theoretically discovers the dynamics of phonon modes of MnBi 2n Te 3n+ 1 family, facilitating utilization of magnetic topological heterostructures.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Materials Data on MnTe by Materials Project

MnTe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mn2+ is bonded to six equivalent Te2- atoms to form a mixture of edge and corner-sharing MnTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Mn–Te bond lengths are 2.88 Å. Te2- is bonded to six equivalent Mn2+ atoms to form a mixture of edge and corner-sharing TeMn6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnTe2 by Materials Project

MnTe2 is Pyrite structured and crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Mn4+ is bonded to six equivalent Te2- atoms to form corner-sharing MnTe6 octahedra. The corner-sharing octahedral tilt angles are 62°. All Mn–Te bond lengths are 2.76 Å. Te2- is bonded in a distorted trigonal planar geometry to three equivalent Mn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnTe by Materials Project

MnTe is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mn2+ is bonded to six equivalent Te2- atoms to form a mixture of edge, face, and corner-sharing MnTe6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Mn–Te bond lengths are 2.85 Å. Te2- is bonded in a 6-coordinate geometry to six equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnTe by Materials Project

MnTe is Hausmannite-like structured and crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are four inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to six Te2- atoms to form distorted MnTe6 octahedra that share corners with nine MnTe4 tetrahedra, edges with six MnTe6 octahedra, and a faceface with one MnTe4 tetrahedra. There are a spread of Mn–Te bond distances ranging from 2.76–3.15 Å. In the second Mn2+ site, Mn2+ is bonded to four Te2- atoms to form MnTe4 tetrahedra that share corners with nine MnTe6 octahedra, corners with two equivalent MnTe4 tetrahedra, edges with two equivalent MnTe4 tetrahedra, and a faceface with one MnTe6 octahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of Mn–Te bond distances ranging from 2.61–2.71 Å. In the third Mn2+ site, Mn2+ is bonded to four Te2- atoms to form MnTe4 tetrahedra that share corners with nine MnTe6 octahedra, corners with two equivalent MnTe4 tetrahedra, edges with two equivalent MnTe4 tetrahedra, and a faceface with one MnTe6 octahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of Mn–Te bond distances ranging from 2.61–2.70 Å. In the fourth Mn2+ site, Mn2+ is bonded to six Te2- atoms to form distorted MnTe6 octahedra that share corners with nine MnTe4 tetrahedra, edges with six MnTe6 octahedra, and a faceface with one MnTe4 tetrahedra. There are a spread of Mn–Te bond distances ranging from 2.77–3.14 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to four Mn2+ atoms to form a mixture of distorted corner and edge-sharing TeMn4 trigonal pyramids. In the second Te2- site, Te2- is bonded in a 6-coordinate geometry to six Mn2+ atoms. In the third Te2- site, Te2- is bonded to four Mn2+ atoms to form a mixture of distorted corner and edge-sharing TeMn4 trigonal pyramids. In the fourth Te2- site, Te2- is bonded in a 6-coordinate geometry to six Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnTe by Materials Project

MnTe is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Mn2+ is bonded to four equivalent Te2- atoms to form corner-sharing MnTe4 tetrahedra. All Mn–Te bond lengths are 2.77 Å. Te2- is bonded to four equivalent Mn2+ atoms to form corner-sharing TeMn4 tetrahedra.

36 MATERIALS SCIENCE↗