High-quality single crystals of MnBi2Te4 are grown for the first time by slow cooling within a narrow range between the melting points of Bi2Te3 (586 °C) and MnBi2Te4 (600 °C). Single-crystal X-ray diffraction and electron microscopy reveal ubiquitous antisite defects in both cation sites and, possibly, Mn vacancies (Mn0.85(3)Bi2.10(3)Te4). Thermochemical studies complemented with high-temperature X-ray diffraction establish a limited high-temperature range of phase stability and metastability at room temperature. Nevertheless, the synthesis of MnBi2Te4 can be scaled-up as powders can be obtained at subsolidus temperatures and quenched at room temperature. Bulk samples exhibit long-range antiferromagnetic ordering below 24 K. The Mn(II) out-of-plane magnetic state is confirmed by the magnetization, X-ray photoemission, X-ray absorption, and linear dichroism measurements. The compound shows a metallic type of resistivity in the range 4.5–300 K and is an n-type conductor that reaches a thermoelectric figure of merit up to ZT = 0.17. Angle-resolved photoemission experiments show a surface state forming a gapped Dirac cone, thus strengthening MnBi2Te4 as a promising candidate for the intrinsic magnetic topological insulator, in accordance with theoretical predictions. The developed synthetic protocols enable further experimental studies of a crossover between magnetic ordering and nontrivial topology in bulk MnBi2Te4.
首次通过在Bi2Te3(586°C)和MnBi2Te4(600°C)的熔点之间狭窄范围内的缓慢冷却,生长出高质量的MnBi2Te4单晶。单晶X射线衍射和电子显微镜揭示了阳离子位置上普遍存在的错位缺陷,可能还有Mn空位(Mn0.85(3)Bi2.10(3)Te4)。热
化学研究与高温X射线衍射相结合,确定了有限的高温相稳定性和室温亚稳态范围。尽管如此,MnBi2Te4的合成可以扩大规模,因为粉末可以在亚固相温度下获得,并在室温下淬火。大块样品在低于24 K时表现出长程反
铁磁有序。通过磁化、X射线光电子、X射线吸收和线性二向色性测量,证实了Mn(II)的平面外磁态。该化合物在4.5-300 K范围内表现出
金属型的电阻率,是一种n型导体,其热电优值高达ZT = 0.17。角分辨光电子实验显示表面态形成了一个带隙的狄拉克锥,从而加强了MnBi2Te4作为内禀磁性拓扑绝缘体的候选材料的地位,这与理论预测一致。所开发的合成方案使得进一步研究大块MnBi2Te4中磁有序与非平凡拓扑之间的过渡成为可能。