Conductive properties of heavy-rare-earth A2Ir2O7 iridates synthesized by the CsCl-flux method

Staško, Daniel; Vlášková, K.; Proschek, Petr; Klicpera, M.

doi:10.1016/j.jpcs.2023.111268

Cited by 5 publications

(4 citation statements)

References 41 publications

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“…A significant increase of T CW was revealed in the A = Tm and Yb members. Although the same trend has been observed in heavy rare-earth A 2 Ir 2 O 7 iridates [3,57,58] crystallising in pyrochlore structure, the pyrochlore A 2 Ti 2 O 7 titanates reveal a different nonmonotonic behaviour [59]. We ascribe large negative values of determined T CW , rather than to low-energy magnetic interactions affected by crystal field, to high-energy crystal field levels only.…”

Section: Magnetisation Measurementssupporting

confidence: 74%

Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇

Vojtasová,

Staško,

Hájek

et al. 2024

J. Phys.: Condens. Matter

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Rare-earth A 2Zr2O7 zirconates have attracted considerable attention of the scientific community for their complex magnetic, electronic and material properties applicable in modern technologies. Light rare-earth members of the series, crystallising in the so-called pyrochlore variant of cubic crystal structure, have been studied in detail. HeavierA 2Zr2O7 compounds have been investigated mainly from the material properties viewpoint, focussing on their thermal properties and stability at high temperature and pressure. Low-temperature studies were mostly missing until recently. We present the low-temperature magnetic and thermodynamic properties of A 2Zr2O7 with A = Y, La, Nd, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu, well covering the whole series,the heavy rare-earth zirconates newly synthesised by high-temperature sintering and melting methods. X-ray diffraction reveals/confirms the ordered pyrochlore structure in light members, the disordered cubic structure of the defect-fluorite type in A 2Zr2O7 with A = Y, Gd – Yb, and the lower symmetry rhombohedral structure in the end-member Lu2Zr2O7. The specific heat of investigated compounds is dominated by the low-temperature anomaly associated with the magnetic ordering, long-range in light rare-earth zirconates, and short-range in heavier members. Effective magnetic moment in studied compounds, determined by fitting the magnetisation data to the Curie-Weiss formula, is in good agreement with the value of the A 3+ free ion. The magnetic properties were documented to be strongly influenced by the frustration of magnetic moments, connected to atomic disorder on the geometrically frustrated lattice. The experimental results are discussed in the framework of previous studies on A 2Zr2O7 zirconates, as well as other A 2 B 2O7 compounds.

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Section: Magnetisation Measurementssupporting

confidence: 74%

Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇

Vojtasová,

Staško,

Hájek

et al. 2024

J. Phys.: Condens. Matter

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“…On the other hand, pronounced anomalies have been found in specific heat of RE 2 Ir 2 O 7 . These anomalies are related rather to magnetic transitions, and the latter induce MIT in RE 2 Ir 2 O 7 [6,7]. Given the absence of visible magnetic transition, one could argue the nature of the possible MIT in Hg 2 Ir 2 O 7 .…”

Section: (B) a Modifiedmentioning

confidence: 99%

“…Antiferromagnetic insulator Sr 2 IrO 4 with Ir 4+ (5d 5 ) shows SOC-dominated j eff = 1/2 Mott state [5]. The family of rare-earth RE 2 Ir 2 O 7 (RE = from Nd to Lu) with Ir 5+ (5d 4 ) exhibits metal/semiconductor-to-insulator transitions (MIT) with decreasing temperature [6][7][8]. The insulating state seems to be induced by the magnetic ordering of the Ir sublattice, and the transition temperatures moving to higher values were observed from A = Nd to Lu [8][9][10][11].…”

mentioning

confidence: 99%

“…The insulating state seems to be induced by the magnetic ordering of the Ir sublattice, and the transition temperatures moving to higher values were observed from A = Nd to Lu [8][9][10][11]. The reason is that magnetic ordering is influenced by interatomic distances and the change in the Ir-O-Ir angle, which are in turn connected to the size of rare-earth cations [6,7]. Additionally, the strong spin-orbit coupling of 5d-electron and weak electron correlations between extended 5d-orbitals in these RE 2 Ir 2 O 7 could generate various complex states, e.g., topological phases, Weyl semi-metal or topological Mott insulator [7,[12][13][14][15][16]].…”

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confidence: 99%

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Anomalous metallic conductivity and short-range ferromagnetic correlation in high-pressure synthesized pyrochlore

Zhao,

Deng,

Zhang

et al. 2024

EPL

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Iridates show fascinating properties due to the unpredictable ground states of their Ir cations. Generally, Ir5+(5d4) systems exhibit insulating nonmagnetic states owing to the strong spin-orbit coupling (SOC). Herein a new pyrochlore iridates Hg2Ir2O7 with an Ir5+ charge state synthesized by high-pressure technique is reported. Hg2Ir2O7 crystallizes in the typical cubic pyrochlore crystal structure. The Ir5+ valence state is evidenced by the XAS spectrum. Surprisingly, Hg2Ir2O7 displays short-range ferromagnetic correlations at low temperatures as evidenced by S-shape field-dependent magnetization curves, positive magnetoresistance, and magnetic excitations in specific heat. Furthermore, it also shows metallic conduction and large electron component of specific heat. These results all indicate that Ir5+ in Hg2Ir2O7 deviates from SOC-dominated insulating nonmagnetic states.

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Robustness of the pyrochlore structure in rare-earth A2Ir2O7 iridates and pressure-induced structural transformation in IrO2

Staško,

Vlášková,

Kancko

et al. 2024

Ceramics International

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Conductive properties of heavy-rare-earth A2Ir2O7 iridates synthesized by the CsCl-flux method

Cited by 5 publications

References 41 publications

Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇

Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇

Anomalous metallic conductivity and short-range ferromagnetic correlation in high-pressure synthesized pyrochlore

Robustness of the pyrochlore structure in rare-earth A2Ir2O7 iridates and pressure-induced structural transformation in IrO2

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Conductive properties of heavy-rare-earth A2Ir2O7 iridates synthesized by the CsCl-flux method

Cited by 5 publications

References 41 publications

Low-temperature properties of magnetically frustrated rare-earth zirconates A 2Zr2O7

Low-temperature properties of magnetically frustrated rare-earth zirconates A 2Zr2O7

Anomalous metallic conductivity and short-range ferromagnetic correlation in high-pressure synthesized pyrochlore

Robustness of the pyrochlore structure in rare-earth A2Ir2O7 iridates and pressure-induced structural transformation in IrO2

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Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇

Low-temperature properties of magnetically frustrated rare-earth zirconates A ₂Zr₂O₇