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Title: Uncovering the behavior of Hf 2 Te 2 P and the candidate Dirac metal Zr 2 Te 2 P
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Journal Name:
Journal of Physics: Condensed Matter
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IOP Publishing
Sponsoring Org:
National Science Foundation
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  1. Abstract Results are reported for Mn intercalated Zr 2 Te 2 P, where x-ray diffraction , energy dispersive spectroscopy, and transmission electron microscopy measurements reveal that the van der Waals bonded Te–Te layers are partially filled by Zr and Mn ions. This leads to the chemical formulas Zr 0.07 Zr 2 Te 2 P and Mn 0.06 Zr 0.03 Zr 2 Te 2 P for the parent and substituted compounds, respectively. The impact of the Mn ions is seen in the anisotropic magnetic susceptibility, where Curie–Weiss fits to the data indicate that the Mn ions are in the divalent state. Heat capacity and electrical transport measurements reveal metallic behavior, but the electronic coefficient of the heat capacity ( γ Mn ≈ 36.6 mJ (mol·K 2 ) −1 ) is enhanced by comparison to that of the parent compound. Magnetic ordering is seen at T M ≈ 4  K, where heat capacity measurements additionally show that the phase transition is broad, likely due to the disordered Mn distribution. This transition also strongly reduces the electronic scattering seen in the normalized electrical resistance. These results show that Mn substitution simultaneously introduces magnetic interactions and tunes the electronic state, which improves prospects for inducingmore »novel behavior in Zr 2 Te 2 P and the broader family of ternary tetradymites.« less
  2. Abstract MnBi 2 Te 4 /(Bi 2 Te 3 ) n materials system has recently generated strong interest as a natural platform for the realization of the quantum anomalous Hall (QAH) state. The system is magnetically much better ordered than substitutionally doped materials, however, the detrimental effects of certain disorders are becoming increasingly acknowledged. Here, from compiling structural, compositional, and magnetic metrics of disorder in ferromagnetic (FM) MnBi 2 Te 4 /(Bi 2 Te 3 ) n it is found that migration of Mn between MnBi 2 Te 4 septuple layers (SLs) and otherwise non-magnetic Bi 2 Te 3 quintuple layers (QLs) has systemic consequences—it induces FM coupling of Mn-depleted SLs with Mn-doped QLs, seen in ferromagnetic resonance as an acoustic and optical resonance mode of the two coupled spin subsystems. Even for a large SL separation ( n ≳ 4 QLs) the structure cannot be considered as a stack of uncoupled two-dimensional layers. Angle-resolved photoemission spectroscopy and density functional theory studies show that Mn disorder within an SL causes delocalization of electron wave functions and a change of the surface band structure as compared to the ideal MnBi 2 Te 4 /(Bi 2 Te 3 ) n . Thesemore »findings highlight the critical importance of inter- and intra-SL disorder towards achieving new QAH platforms as well as exploring novel axion physics in intrinsic topological magnets.« less