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arXiv 2102.08979cond-mat.str-elcond-mat.mtrl-sci
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用Fe、In或Ni掺杂来调谐可果美金属CoSn的平带

Tuning the flat bands of the kagome metal CoSn with Fe, In, or Ni doping

B. C. Sales, W. R. Meier, A. F. May, J. Xing, J. -Q Yan, S. Gao, Y. H. Liu, M. B. Stone, A. D. Christianson, Q. Zhang, M. A. McGuire

摘要:

CoSn是一种泡利顺磁体,具有相对平坦的d-带,中心在费米能量Ef以下约100 meV。用X射线和中子散射、磁化率和磁化强度、交流磁化率、比热和电阻率测量研究了轻掺杂Fe、In或Ni的CoSn单晶。在刚性能带近似下,掺杂几个百分比的Fe或In的空穴应该使平带更靠近Ef,而掺杂Ni的电子应该使平带更远离Ef。我们提供的证据表明,这种情况确实发生。Fe和In掺杂驱动CoSn朝向磁性,而Ni掺杂抑制CoSn已经很弱的磁性响应。对于Fe与In掺杂,所得到的基态是不同的。对于Fe掺杂的晶体Co 1-xFexSn(0.02 < x < 0.27),磁性和比热数据与自旋玻璃的形成一致,玻璃化转变温度Tg范围为1 K(x=0.02)至10 K(x= 0.27)。粉末和单晶中子衍射发现没有证据的长程磁低于Tg与x = 0.17。对于In掺杂的晶体CoSn 1-yIny,磁化率和索末菲系数γ相对于纯CoSn显著增加,但对于0.05 < y < 0.2没有明显的磁转变指示。掺杂有Ni(Co0.93Ni0.07Sn)的CoSn晶体具有比纯CoSn显著更小的磁化率和γ,与远离Ef的平坦带一致。

英文摘要:

CoSn is a Pauli paramagnet with relatively flat d-bands centered about 100 meV below the Fermi energy Ef. Single crystals of CoSn lightly doped with Fe, In, or Ni are investigated using x-ray and neutron scattering, magnetic susceptibility and magnetization, ac susceptibility, specific heat and resistivity measurements. Within the rigid band approximation, hole doping with a few percent of Fe or In should move the flat bands closer to Ef, whereas electron doping with Ni should move the flat bands further away from Ef. We provide evidence that this indeed occurs. Fe and In doping drive CoSn toward magnetism, while Ni doping suppresses CoSn's already weak magnetic response. The resulting ground state is different for Fe versus In doping. For Fe-doped crystals, Co1-xFexSn, with 0.02 < x < 0.27, the magnetic and specific heat data are consistent with the formation of a spin glass, with a glass transition temperature, Tg, ranging from 1 K for x=0.02 to 10 K for x= 0.27. Powder and single crystal neutron diffraction found no evidence of long-range magnetic order below Tg with x = 0.17. For In-doped crystals, CoSn1-yIny, both the magnetic susceptibility and the Sommerfeld coefficient, gamma, increase substantially relative to pure CoSn, but with no clear indication of a magnetic transition for 0.05 < y < 0.2. CoSn crystals doped with Ni (Co0.93Ni0.07Sn) have a significantly smaller magnetic susceptibility and gamma than pure CoSn, consistent with the flat bands further from Ef.

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