Isoelectronic perturbations to $f$-$d$-electron hybridization and the enhancement of hidden order in URu${}_2$Si${}_2$

Abstract

Electrical resistivity measurements were performed on single crystals of URu${}_2-x$Os${}_x$Si${}_2$ 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 to LMAFM phase transition. We compare the $T(x)$, $T(P)$ phase behavior reported here for the URu${}_2-x$Os${}_x$Si${}_2$ system with previous reports of enhanced HO in URu${}_2$Si${}_2$ upon tuning with $P$, or similarly in URu${}_2-x$Fe${}_x$Si${}_2$ upon tuning with positive $P_{ch}$($x$). It is noted 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 URu${}_2$Si${}_2$. 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-5$f$- and transition metal $d$-electron states which leads to electronic instability in the paramagnetic phase and a concurrent stability of HO (and LMAFM) in URu${}_2$Si${}_2$. Calculations in the tight binding approximation are included to determine the strength of hybridization between the U-5$f$ electrons and each of the isoelectronic transition metal $d$-electron states of Fe, Ru, and Os.

15 pages, 11 figures

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Cited by in corpus (6)

• Fe substitution in URu${}_2$Si${}_2$: singlet magnetism in an extended Doniach phase diagram
• Heat capacity of URu${}_{2-x}$Os${}_x$Si${}_2$ at low temperatures
• The Symmetry Principle in Condensed Matter Physics (I)
• Collinear antiferromagnetic order in URu${}_2$Si${}_{2-x}$P${}_x$ revealed by neutron diffraction
• Unified Theory of Hastatic order and Antiferromagnetism in URu${}_2$Si${}_2$
• Magnetic transitions induced by pressure and magnetic field in a two-orbital $5f$-electron model in cubic and tetragonal lattices