Layered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: towards multifunctional materials

Souchay, Daniel; Nentwig, Markus; Günther, Daniel; Keilholz, Simon; Boor, Johannes de; Zeugner, Alexander; Isaeva, Anna; Ruck, Michael; Wolter, A. U. B.; Büchner, B.; Oeckler, Oliver

doi:10.1039/c9tc00979e

Cited by 38 publications

(46 citation statements)

References 68 publications

(74 reference statements)

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“…Table 1 also shows that defect densities and the Mn deficiency increases from MnBi 2 Te 4 to MnBi 4 Te 7 , consistent with the trend observed experimentally. [ 5f,7b,15 ] Based on calculated formation energies of

{Mn}_{Bi}^{-}

on different sites in MnBi 4 Te 7 , it can be shown that, under thermal equilibrium, about 5/6 of

{Mn}_{Bi}^{-}

are located in the QL while the other 1/6 are in the SL.…”

Section: Resultsmentioning

confidence: 99%

“…Indeed, previous experiments showed an increased Mn deficiency in MnBi 6 Te 10 . [ 7b,15 ] The strain‐induced antisite formation as discussed above may also explain the observation of a few percent of Te Se and Se Te antisites in the topological insulator Bi 2 Te 2 Se, which has an ordered crystal structure with the small‐sized Se occupies the middle layer of a QL. [ 20 ]…”

Section: Discussionmentioning

confidence: 99%

“…Finally, our defect calculations and transport measurements suggest that several assumptions made in the experimental composition analysis [ 5f,7b,15 ] could lead to significant errors. 1) The charge state of Bi ions was assumed to be +3 when the charge neutrality condition was applied in the composition analysis.…”

Section: Discussionmentioning

confidence: 99%

“…3) The Mn vacancy,

V_{Mn}^{2 -}

, which was assumed as an important defect in previous composition analyses, actually has a relatively high formation energy in both MnBi 2 Te 4 and MiBi 4 Te 7 (Figure 2) and should not be a major factor behind the experimentally observed Mn deficiency in MnBi 4 Te 7 . [ 5f,7b,15 ] The neglect of the negatively charged

{Bi}_{Te}^{-}

and free electrons could increase the estimated density of positively charged defects

({Bi}_{Mn}^{+})

, leading to artificially high Mn deficiencies in composition analyses.…”

Section: Discussionmentioning

confidence: 99%

“…The Mn deficiencies were estimated to be 15–20% in MnBi 4 Te 7 and 19–25% in MnBi 6 Te 10 . [ 5f,7b,15 ] Such high defect densities not only affect the Fermi level but could also influence the magnetic and topological properties. For example, a high density of magnetic defects may affect the surface magnetism and the opening of the surface energy gap.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Yan

Cooper

et al. 2020

Adv Funct Materials

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MnBi 2 Te 4 and MnBi 4 Te 7 are intrinsic antiferromagnetic topological insulators, offering a promising materials platform for realizing exotic topological quantum states. However, high densities of intrinsic defects in these materials not only cause bulk metallic conductivity, preventing the measurement of quantum transport in surface states, but may also affect magnetism and topological properties. In this paper, systematic density functional theory calculations reveal specific material chemistry and growth conditions that determine the defect formation and dopant incorporation in MnBi 2 Te 4 and MnBi 4 Te 7. The large strain induced by the internal heterostructure promotes the formation of large-size-mismatched antisite defects and substitutional dopants. The results here show that the abundance of antisite defects is responsible for the observed n-type metallic conductivity. A Te-rich growth condition is predicted to reduce the bulk free electron density, which is confirmed by experimental synthesis and transport measurements in MnBi 2 Te 4. Furthermore, Na doping is proposed to be an effective acceptor dopant to pin the Fermi level within the bulk band gap to enable the observation of surface quantum transport. The defect engineering and doping strategies proposed here should stimulate further studies for improving synthesis and for manipulating magnetic and topological properties in MnBi 2 Te 4 , MnBi 4 Te 7 , and related magnetic topological insulators.

show abstract

{Mn}_{Bi}^{-}

on different sites in MnBi 4 Te 7 , it can be shown that, under thermal equilibrium, about 5/6 of

{Mn}_{Bi}^{-}

are located in the QL while the other 1/6 are in the SL.…”

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…3) The Mn vacancy,

V_{Mn}^{2 -}

{Bi}_{Te}^{-}

and free electrons could increase the estimated density of positively charged defects

({Bi}_{Mn}^{+})

, leading to artificially high Mn deficiencies in composition analyses.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Yan

Cooper

et al. 2020

Adv Funct Materials

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Intermixing‐Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi₆Te₁₀

et al. 2023

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The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures.

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Ubiquitous Order‐Disorder Transition in the Mn Antisite Sublattice of the (MnBi₂Te₄)(Bi₂Te₃)_n Magnetic Topological Insulators

Sahoo,

Onuorah,

Folkers

et al. 2024

Advanced Science

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Magnetic topological insulators (TIs) herald a wealth of applications in spin‐based technologies, relying on the novel quantum phenomena provided by their topological properties. Particularly promising is the (MnBi2Te4)(Bi2Te3)n layered family of established intrinsic magnetic TIs that can flexibly realize various magnetic orders and topological states. High tunability of this material platform is enabled by manganese–pnictogen intermixing, whose amounts and distribution patterns are controlled by synthetic conditions. Here, nuclear magnetic resonance and muon spin spectroscopy, sensitive local probe techniques, are employed to scrutinize the impact of the intermixing on the magnetic properties of (MnBi2Te4)(Bi2Te3)n and MnSb2Te4. The measurements not only confirm the opposite alignment between the Mn magnetic moments on native sites and antisites in the ground state of MnSb2Te4, but for the first time directly show the same alignment in (MnBi2Te4)(Bi2Te3)n with n = 0, 1 and 2. Moreover, for all compounds, the static magnetic moment of the Mn antisite sublattice is found to disappear well below the intrinsic magnetic transition temperature, leaving a homogeneous magnetic structure undisturbed by the intermixing. The findings provide a microscopic understanding of the crucial role played by Mn–Bi intermixing in (MnBi2Te4)(Bi2Te3)n and offer pathways to optimizing the magnetic gap in its surface states.

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Layered manganese bismuth tellurides with GeBi₄Te₇- and GeBi₆Te₁₀-type structures: towards multifunctional materials

Abstract: Non-stoichiometry is the key to single-phase layered compounds in the system Mn/Bi/Te, which is essential to evaluate their multifunctional properties.

Cited by 38 publications

References 68 publications

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Intermixing‐Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi₆Te₁₀

Ubiquitous Order‐Disorder Transition in the Mn Antisite Sublattice of the (MnBi₂Te₄)(Bi₂Te₃)_n Magnetic Topological Insulators

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Layered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: towards multifunctional materials

Abstract: Non-stoichiometry is the key to single-phase layered compounds in the system Mn/Bi/Te, which is essential to evaluate their multifunctional properties.

Cited by 38 publications

References 68 publications

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi2Te4 and MnBi4Te7 by Defect Engineering and Chemical Doping

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi2Te4 and MnBi4Te7 by Defect Engineering and Chemical Doping

Intermixing‐Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi6Te10

Ubiquitous Order‐Disorder Transition in the Mn Antisite Sublattice of the (MnBi2Te4)(Bi2Te3)n Magnetic Topological Insulators

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Layered manganese bismuth tellurides with GeBi₄Te₇- and GeBi₆Te₁₀-type structures: towards multifunctional materials

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi₂Te₄ and MnBi₄Te₇ by Defect Engineering and Chemical Doping

Intermixing‐Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi₆Te₁₀

Ubiquitous Order‐Disorder Transition in the Mn Antisite Sublattice of the (MnBi₂Te₄)(Bi₂Te₃)_n Magnetic Topological Insulators