Electrical resistivity measurements were performed on single crystals of URu_2–xOs_xSi₂ up to x = 0.28 under hydrostatic pressure up to P = 2 GPa. As the Os concentration, x, is increased, 1) the lattice expands, creating an effective negative chemical pressure P_ch(x); 2) the hidden-order (HO) phase is enhanced and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase; and 3) less external pressure P_c is required to induce the HO→LMAFM phase transition. We compare the behavior of the T(x, P) phase boundary reported here for the URu_2-xOs_xSi₂ system with previous reports of enhanced HO in URu₂Si₂ upon tuning with P or similarly in URu_2–xFe_xSi₂ upon tuning with positive P_ch(x). It is noteworthy that pressure, Fe substitution, and Os substitution are the only known perturbations that enhance the HO phase and induce the first-order transition to the LMAFM phase in URu₂Si₂. We present a scenario in which the application of pressure or the isoelectronic substitution of Fe and Os ions for Ru results in an increase in the hybridization of the U-5f-electron and transition metal d-electron states which leads to electronic instability in the paramagnetic phase and the concurrent formation of HO (and LMAFM) in URu₂Si₂. Calculations in the tight-binding approximation are included to determine the strength of hybridization between the U-5f-electron states and the d-electron states of Ru and its isoelectronic Fe and Os substituents in URu₂Si₂.

在高达P = 2 GPa 的静水压力下，对高达x = 0.28的 URu _{2– x} Os _x Si ₂单晶进行电阻率测量。随着 Os 浓度x的增加，1) 晶格膨胀，产生有效的负化学压力P _ch ( x )；2) 隐藏阶 (HO) 相位增强，系统被驱动到大力矩反铁磁 (LMAFM) 相位；3) 需要较少的外部压力P _c来诱导 H2O→LMAFM 相变。我们比较T ( x ,P ) 此处报告的 URu _{2- x} Os _x Si ₂系统的相界，之前有报道称在用P调谐时URu ₂ Si ₂中的 H2O 增强，或在用正P _ch调谐时在 URu _{2– x} Fe _x Si _{2 中}类似地（× )。值得注意的是，压力、Fe 取代和 Os 取代是唯一已知的可增强 H2O 相并诱导 URu ₂ Si _{2 中}LMAFM 相的一级转变的扰动. 我们提出了一个场景，其中施加压力或 Fe 和 Os 离子对 Ru 的等电子取代导致 U-5 f电子和过渡金属d电子态的杂化增加，从而导致电子不稳定顺磁相和在 URu ₂ Si _{2 中}同时形成 H2O（和 LMAFM）。包括紧束缚近似中的计算，以确定 U-5 f电子态和Ru的d电子态之间的杂化强度及其在 URu ₂ Si _{2 中的}等电子 Fe 和 Os 取代基。