アイテム詳細

要旨

CuTeO4 has been proposed as a crystallographically distinct, yet electronic structure analog, of the superconducting cuprates. Here, we present a detailed characterization of the physical properties of CuTeO4 to address this proposal. Fitting of magnetic susceptibility data indicates unexpected quasi-one-dimensional, antiferromagnetic correlations at high temperature, with a nearest-neighbor Heisenberg exchange of J1=164(5) K. Low-temperature heat capacity measurements reveal a sizable T-linear contribution of γ=9.58(8) mJ mol-1K-2, qualitatively consistent with expectations for a S=1/2, uniform, Heisenberg spin chain. Below T≈40 K, the susceptibility shows an upturn inconsistent with quasi-one-dimensional behavior. While heat capacity measurements show no signs of magnetic order down to low-temperature, the upturn in the magnetic susceptibility coincides with the emergence of a diffuse peak (centered at |Q - |≈0.7 Å) in the neutron diffraction data, indicative of persistent, short-range, antiferromagnetic order with a correlation length of ζ=10.1(9) Å at T=10 K. The onset of nonlinearity and hysteresis in the isothermal magnetization curves suggests the presence of a small ferromagnetic component. This persistent, short-range order is understood in the context of structural modeling of the x-ray and neutron diffraction data that show the presence of a significant density of stacking faults. No evidence for substantive dopability is observed and CuTeO4 appears, qualitatively, to have a larger band gap than predicted by density functional theory. We ascribe this finding to the inductive withdrawal effect from high-valence Te and suggest that superconductivity in copper tellurates is more likely to be found in compounds with a decreased reductive withdrawal effect from Te. © 2024 American Physical Society.