Quasi-Two-Dimensional Heterostructures (KM1 – xTe)(LaTe3) (M = Mn and Zn) with Charge Density Waves

摘要

M _(1 – x )Te_(4) (M = Mn and Zn; x ≈ 0.35) featuring two chemically distinct alternating layers LaTe_(3) and KM _(1 – x )Te. Their crystal structures are incommensurate, determined by single X-ray diffraction for the Mn compound and a transmission electron microscope study for the Zn compound. KLaMn_(1 – x )Te_(4) crystallizes in the orthorhombic superspace group Pmnm (01/2γ)s 00 with lattice parameters a = 4.4815(3) Å, b = 21.6649(16) Å, and c = 4.5220(3) Å. It exhibits charge density wave order at room temperature with a modulation wave vector q = 1/2b * + 0.3478c * originating from electronic instability of Te-square nets in LaTe_(3) layers. The Mn analog exhibits a cluster spin glass behavior with spin freezing temperature T _(f) ≈ 5 K attributed to disordered Mn vacancies and competing magnetic interactions in the Mn_(1 – x )Te layers. The Zn analog also has charge density wave order at room temperature with a similar q -vector having the c * component ∼0.346 confirmed by selected-area electron diffraction. Electron transfer from KM _(1 – x )Te to LaTe_(3) layers exists in KLaM _(1 – x )Te_(4), leading to an enhanced electronic specific heat coefficient. The resistivities of KLaM _(1 – x )Te_(4) (M = Mn and Zn) exhibit metallic behavior at high temperatures and an upturn at low temperatures, suggesting partial localization of carriers in the LaTe_(3) layers with some degree of disorder associated with the M atom vacancies in the M _(1 – x )Te layers.>