Isoelectronic perturbations to f-d-electron hybridization and the enhancement of hidden order in URu2Si2

Electrical resistivity measurements were performed on single crystals of URu2–xOsxSi2 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 Pch(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 Pc is required to induce the HO→LMAFM phase transition. We compare the behavior of the T(x, P) phase boundary reported here for the URu2-xOsxSi2 system with previous reports of enhanced HO in URu2Si2 upon tuning with P or similarly in URu2–xFexSi2 upon tuning with positive Pch(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.

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Heisenberg spins on an anisotropic triangular lattice: PdCrO2 under uniaxial stress

New Journal of Physics ◽

10.1088/1367-2630/ac4280 ◽

2021 ◽

Author(s):

Dan Sun ◽

Dmitry Sokolov ◽

Richard Waite ◽

Seunghyun Khim ◽

Pascal Manuel ◽

...

Keyword(s):

Neutron Diffraction ◽

Triangular Lattice ◽

Ground State ◽

Nearest Neighbor ◽

Magnetic Order ◽

Uniaxial Stress ◽

Rate Of Change ◽

Resistivity Measurements ◽

First Order ◽

First Order Transition

Abstract When Heisenberg spins interact antiferromagnetically on a triangular lattice and nearest-neighbor interactions dominate, the ground state is 120◦ antiferromagnetism. In this work, we probe the response of this state to lifting the triangular symmetry, through investigation of the triangular antiferromagnet PdCrO2 under uniaxial stress by neutron diffraction and resistivity measurements. The periodicity of the magnetic order is found to change rapidly with applied stress; the rate of change indicates that the magnetic anisotropy is roughly forty times the stress-induced bond length anisotropy. At low stress, the incommensuration period becomes extremely long, on the order of 1000 lattice spacings; no locking of the magnetism to commensurate periodicity is detected. Separately, the magnetic structure is found to undergo a first-order transition at a compressive stress of ∼0.4 GPa, at which the interlayer ordering switches from a double- to a single-q structure.

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Edge singularity in tight binding approximation

Journal de Physique ◽

10.1051/jphys:019720033011-120108100 ◽

1972 ◽

Vol 33 (11-12) ◽

pp. 1081-1088 ◽

Cited By ~ 2

Author(s):

P. Joyes

Keyword(s):

Tight Binding ◽

Tight Binding Approximation ◽

Edge Singularity

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First-order transition features of the triangular Ising model with nearest- and next-nearest-neighbor antiferromagnetic interactions

Physica A Statistical Mechanics and its Applications ◽

10.1016/j.physa.2007.04.051 ◽

2007 ◽

Vol 383 (2) ◽

pp. 351-371 ◽

Cited By ~ 14

Author(s):

A. Malakis ◽

N.G. Fytas ◽

P. Kalozoumis

Keyword(s):

Ising Model ◽

Nearest Neighbor ◽

Order Transition ◽

First Order ◽

First Order Transition

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The Effect of Topology on Phase Behavior under Confinement

Processes ◽

10.3390/pr9071220 ◽

2021 ◽

Vol 9 (7) ◽

pp. 1220

Author(s):

Arnout M. P. Boelens ◽

Hamdi A. Tchelepi

Keyword(s):

Phase Behavior ◽

Density Functional ◽

Capillary Condensation ◽

Good Description ◽

Functional Theory ◽

Minkowski Functionals ◽

First Order ◽

Lennard Jones ◽

And Topology ◽

First Order Transition

This work studies how morphology (i.e., the shape of a structure) and topology (i.e., how different structures are connected) influence wall adsorption and capillary condensation under tight confinement. Numerical simulations based on classical density functional theory (cDFT) are run for a wide variety of geometries using both hard-sphere and Lennard-Jones fluids. These cDFT computations are compared to results obtained using the Minkowski functionals. It is found that the Minkowski functionals can provide a good description of the behavior of Lennard-Jones fluids down to small system sizes. In addition, through decomposition of the free energy, the Minkowski functionals provide a good framework to better understand what are the dominant contributions to the phase behavior of a system. Lastly, while studying the phase envelope shift as a function of the Minkowski functionals it is found that topology has a different effect depending on whether the phase transition under consideration is a continuous or a discrete (first-order) transition.

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