Annealing effect on crystal structure, carrier concentration, and magnetism inone-layer hole-doped T*-type cuprates Pr1.6Sr0.4CuO4−δ

We investigated the effect of annealing on the crystal structure, effective hole concentration, and magnetic properties of T*-type cuprates Pr_1.6Sr_0.4CuO_4−δ (PSCO) using neutron powder diffraction, X-ray absorption spectroscopy, and muon spin rotation. A significant number of oxygen vacancies were observed at both the apical and in-plane oxygen sites in the Ar-annealed (Ar-AN), as-sintered (AS), and high-pressure O₂-annealed (O₂-AN) PSCO compounds. Our experiments reveal a noticeable reduction in the effective hole concentration, shifting from the heavily-doped to lightly-doped region. Furthermore, we observed enhanced static magnetic order in Ar-AN compound, whereas the transition temperature was suppressed in the AS and high-pressure O₂-AN PSCO. The present results demonstrate an exceptional example of lightly-doped T*-type cuprates. In particular, apical oxygen is more sensitive and substantially influenced by annealing, and the enhanced magnetism in reduction annealing reduces the effect of in-plane oxygen scenario under annealing.

本研究采用中子粉末衍射（neutron powder diffraction）、X射线吸收谱学（X-ray absorption spectroscopy）与μ子自旋旋转（muon spin rotation）技术，探究了退火工艺对T*型铜氧化物Pr₁.₆Sr₀.₄CuO₄−δ（简称PSCO）的晶体结构、有效空穴浓度及磁学性能的影响。针对氩气退火（Ar-AN）、原始烧结（AS）及高压氧气退火（O₂-AN）的PSCO样品，研究团队在其轴向氧位点与面内氧位点均观测到大量氧空位。实验结果表明，样品的有效空穴浓度出现显著降低，从重掺杂区域向轻掺杂区域偏移。此外，氩气退火样品的静态磁序得到增强，而原始烧结与高压氧气退火的PSCO样品的磁转变温度则受到抑制。本研究结果为轻掺杂T*型铜氧化物提供了一个极具代表性的案例。具体而言，轴向氧对退火工艺更为敏感，受其影响更为显著；还原退火带来的磁序增强，削弱了退火过程中面内氧位点的作用效应。