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Insights to unusual antiferromagnetic behavior and exchange coupling interactions in Mn23C6
Ze-Kun Yu(于泽坤), Chao Zhou(周超), Kuo Bao(包括), Zhao-Qing Wang(王兆卿), En-Xuan Li(李恩萱), Jin-Ming Zhu(朱金铭), Yuan Qin(秦源), Yu-Han Meng(孟钰涵), Pin-Wen Zhu(朱品文), Qiang Tao(陶强), and Tian Cui(崔田)
Chin. Phys. B, 2025, 34 (3):
037101.
DOI: 10.1088/1674-1056/adaadd
We report the structural, mechanical and electromagnetic properties of the intermetallic compound Mn$_{23}$C$_{6}$. The bulk Mn$_{23}$C$_{6}$ sample was synthesized using high temperature high pressure quenching method (HTHPQM), and investigated in detail by x-ray diffraction, electron microscope, magnetization and electrical resistivity measurements, etc. First-principles calculation based on density functional theory ab intio simulation was carried out to calculate the bonding and electromagnetic properties of Mn$_{23}$C$_{6}$. Based on our experimental and simulated results, the Mn$_{23}$C$_{6}$ in this work is single phase of a faced-centered cubic structure with space group Fm-3$m$ (No. 225). Determined by SEM and TEM, the bulk sample consists of monocrystal Mn$_{23}$C$_{6}$ crystals with 2-15 μm grain sizes, it is the quick quenching method in the synthesizing process that brings such small crystal grain size. Archimedes method gives its density of 7.14 g/cm$^{3}$, 95.74% of its theoretically calculated density 7.458 g/cm$^{3}$. Owing to the abundant Mn 3d electrons and a framework of strongly linked Mn atoms in Mn$_{23}$C$_{6}$, the electrical conductivity is up to $8.47\times 10^{-4}$ $\Omega \cdot $m, which shows that Mn$_{23}$C$_{6}$ is a good conductor. Our magnetic susceptibility analyses reveal a magnetization peak in the $M$-$T$ curve at 104 K, combined with the $M$-$H$ curve and Curie-Weiss law, this peak usually means the transformation between paramagnetic and antiferromagnetic orders. To gain an insight into the mechanism of the magnetic phase transition, we calculated the magnetic properties, and the results show that different from normal antiferromagnetic order, the magnetic orders in Mn$_{23}$C$_{6}$ consist of three parts, the direct ferromagnetic and antiferromagnetic exchange coupling interactions between Mn atoms, and the indirect antiferromagnetic super-exchange interaction between Mn and C atoms. Therefore, we reveal that the Mn$_{23}$C$_{6}$ is a complex magnetic competition system including different magnetic orders and interactions, instead of the normal long-range antiferromagnetic order.
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