Hydrogen impact on magnetic properties of metallic systems

Havela, L.

doi:10.1016/j.jallcom.2021.162721

Cited by 6 publications

(5 citation statements)

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“…On the other hand, we assume an important bonding of the Yb-5d and 6s states with the H-1s states [27], which reduces the density of states at the Fermi level, and the 4f 13 state may become more stable. The 4d states of Pd which is adjacent to H are likely to be filled in the precursor intermetallic already due to the high Pd electronegativity.…”

Section: Discussionmentioning

confidence: 99%

“…This implies that the reduction is due to the impact of H on the RKKY interaction. For example, in the ferromagnetic compound GdNiAl, T N = 62 K decreases to 15 K in the saturated hydride GdNiAlH 1.35 [27]. The influence of hydrogenation on the ordering temperatures approximately following the De Gennes scaling [28] is analogical for other R. However, in compounds like GdTiGe (ferromagnet with T C = 376 K), where Gd form tetrahedra, which are all occupied by H in the hydride, the effect is similarly striking as in pure Gd, reducing T C from 376 K to less than 4 K [29].…”

Section: Introductionmentioning

confidence: 99%

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Heavy-Fermion Properties of Yb2Pd2SnH≈2

Maskova-Cerna,

Bauer,

Giovannini

et al. 2023

Inorganics

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A hydride of Yb2Pd2Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f13) state, as in Yb2Pd2Sn. Specific heat C/T vs. T shows an upturn existing already in Yb2Pd2Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K2 for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heavy-Fermion Properties of Yb2Pd2SnH≈2

Maskova-Cerna,

Bauer,

Giovannini

et al. 2023

Inorganics

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“…As Th has no magnetic moments, the properties are then dependent on the transition metal component T, which has likely the respective d-states hybridized with the 6d states of Th. The reaction to H absorption is then similar to transition-metal systems, which are sensitive to volume expansion similar to the 5f systems (the d-states are band-like), but in this case the support of magnetism is limited by the loss of metallicity for higher H concentrations [27]. The presence of Th may possibly postpone the onset of insulating state, as the Th bonding to H can leave the T sublattice partly intact.…”

Section: Binary Actinide Intermetallicsmentioning

confidence: 92%

“…Based on data from [116] and [125]. Reprinted from [27], Copyright (2022), with permission from Elsevier.…”

Section: Hydrides Of Ternary Compoundsmentioning

confidence: 99%

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Hydrogen in actinides: electronic and lattice properties

Havela

Legut

Kolorenč³

2023

Rep. Prog. Phys.

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Hydrides of actinides, their magnetic, electronic, transport, and thermodynamic properties are discussed within a general framework of H impact on bonding, characterized by volume expansion, affecting mainly the 5f states, and a charge transfer towards H, which influences mostly the 6d and 7s states. These general mechanisms have diverse impact on individual actinides, depending on the degree of localization of their 5f states. Hydrogenation of uranium yields UH2 and UH3, binary hydrides that are strongly magnetic due to a 5f band narrowing and reduction of the 5f‐6d hybridization. Pu hydrides become magnetic as well, mainly as a result of the stabilization of the magnetic 5f 5 state and elimination of the admixture of the non‐magnetic 5f 6 component. Ab‐initio computational analyses, which for example suggest that the ferromagnetism of β‐UH3 is rather intricate involving two non‐collinear sublattices, are corroborated by spectroscopic studies of sputter‐deposited thin films, yielding a clean surface and offering a variability of compositions. It is found that valence‐band photoelectron spectra cannot be compared directly with the 5f n ground‐state density of states. Being affected by electron correlations in the excited final states, they rather reflect the atomic (n‐1) multiplets. Similar tendencies can be identified also in hydrides of binary and ternary intermetallic compounds. H absorption can be used as a tool for fine tuning of electronic structure around a quantum critical point. A new direction is represented by actinide polyhydrides with a potential for high‐temperature superconductivity.

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