Scientists of the Chinese Academy of Sciences have made progress in the research of magnetic topological semi-metallic materials.

Team of Scientists of the Chinese Academy of Sciences-Zhang Changjin, researcher of the High Magnetic Field Science Center of Hefei Institute of Material Science, and Pili's research group have made new progress in the research of magnetic topological semi-metallic materials. Through magnetic and transport measurements and first-principles calculations under strong magnetic fields, researchers have conducted in-depth studies on the magnetic systems of lanthanide metal antimonides such as NdSb and DySb, and found magnetic topological semi-metallic states.

Topological semi-metals are a new class of topological materials with low-energy excited states similar to elementary particles, which are of great significance in scientific cognition and practical applications. Among them, the Dirac point of the Dirac half metal has both crystal symmetry and time reversal symmetry, known"Three-dimensional graphene". If the crystal symmetry or time reversal symmetry is broken, the Dirac point becomes a pair of Waer points, forming a Waer semi-metal. Weyer semi-metals with broken crystal symmetry have been found in TaAs, WTa2 and other systems, while Weyer semi-metals with broken time reversal symmetry have not been found for a long time. The main reason is that angle-resolved photoelectron spectroscopy has great limitations in the study of magnetic materials, and cannot provide a clear electronic structure in the magnetically ordered state. Systems where it is theoretically predicted that magnetic topological semi-metallic states may exist include lanthanide metal antimonides, bismuth oxides, and GdPtBi, Mn3Sn, and the like.

In this work, the researchers used magnetic and transport measurements under strong magnetic fields to studyThe magnetic structure transformation of NdSb, DySb and other materials analyzes the basic information and carrier characteristics of electronic transport under different magnetic structures, and combined with the results of the first-principle energy band calculation, it is found that the anti-ferromagnetic state of NdSb is the Dirac half-metal state, and the ferromagnetic state of DySb is the outer half-metal state. In particular, the negative magnetoresistance caused by chiral anomalies observed on NdSb provides solid evidence for the existence of topological semi-metallic states. NdSb and DySb also provide an ideal carrier for the study of the relationship between magnetism and topology with their controllable magnetic structure.

The transport measurement of this series of work is the first water-cooled magnet in the steady-state strong magnetic field experimental device.The magnetic measurements were carried out on the WM1 and hybrid magnets, and the magnetic measurements were carried out on the magnetic measurement system (VSM) of the second water-cooled magnet WM2.

This work is supported by the National Key R & D Program and the National Natural Science Foundation of China. It is mainly completed by human-made graduate students Wang Yongjian and Liang Dandan. Related research is published inPhysical Review B、APL Materials上。

High field susceptibility, magnetoresistance measurements (top) and negative magnetoresistance measurements (bottom) of NdSb (top left WM2 provides the highest field 25T, top right WM1 provides the highest field 38T)

DySbThe high-field magnetoresistance measurement and energy band calculation results (the upper left hybrid magnet provides the highest field.38.7T）

(Source: Chinese Academy of Sciences)