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Title: Isoelectronic perturbations to f - d -electron hybridization and the enhancement of hidden order in URu 2 Si 2

Electrical resistivity measurements were performed on single crystals of URu2–xOsxSi2up tox= 0.28 under hydrostatic pressure up toP= 2 GPa. As the Os concentration,x, is increased, 1) the lattice expands, creating an effective negative chemical pressurePch(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 pressurePcis required to induce the HO→LMAFM phase transition. We compare the behavior of theT(x,P) phase boundary reported here for the URu2-xOsxSi2system with previous reports of enhanced HO in URu2Si2upon tuning withPor similarly in URu2–xFexSi2upon tuning with positivePch(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 metald-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 thed-electron states of more » Ru and its isoelectronic Fe and Os substituents in URu2Si2.

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Proceedings of the National Academy of Sciences
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Article No. e2026591118
Proceedings of the National Academy of Sciences
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National Science Foundation
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