Epitaxial growth of iridate pyrochlore Nd2Ir2O7 films

Gallagher, James C.; Esser, Bryan D.; Morrow, Ryan; Dunsiger, S. R.; Williams, R. E. A.; Woodward, Patrick M.; McComb, David W.; Yang, Fengyuan

doi:10.1038/srep22282

Cited by 35 publications

(24 citation statements)

References 24 publications

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“…The in-plane epitaxial relationship was verified as CsW2O6 [11 _ 0] || YSZ [11 _ 0]. Note that this epitaxial relationship is identical to that of normal pyrochlore-type iridate films grown on YSZ (111) substrates [17,18]. In addition, Qx values between the film and substrate were identical, indicating that CsW2O6 films were coherently grown on the YSZ lattice.…”

Section: ■ Experimental Sectionmentioning

confidence: 82%

Electronic properties across metal-insulator transition in β -pyrochlore-type CsW2O6 epitaxial films

Soma

Yoshimatsu

Horiba

et al. 2018

Phys. Rev. Materials

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In CsW2O6, which undergoes a metal-insulator transition (MIT) at 213 K, the emergence of exotic properties associated with rattling motion of Cs is expected owing to its characteristic β-pyrochlore-type structure. However, a hurdle for crystal growth hampers elucidation of detailed properties and mechanisms of the MIT. Here we report on the epitaxial growth of β-pyrochlore-type CsW2O6 films and their electronic properties across the MIT. Using pulsed-laser deposition technique, we grew single-crystalline CsW2O6 films exhibiting remarkably lower resistivity compared with a polycrystalline bulk and sharp MIT around 200 K. Negative magnetoresistance and positive Hall coefficient were found, which became pronounced below 200 K. The valence-band and core-levels photoemission spectra indicated the drastic changes across the MIT. In the valence band photoemission spectrum, the finite density of states was observed at the Fermi level in the metallic phase. In contrast, an energy gap appeared in the insulating phase. The split of W 4f core-level spectrum suggested the charge disproportionation of W 5+ and W 6+ in the insulating phase. The change of spectral shape in the Cs 4d core levels reflected the rattling motion of Cs + cations. These results strongly suggest that CsW2O6 is a novel material, in which MIT is driven by the charge disproportionation associated with the rattling motion.

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Section: ■ Experimental Sectionmentioning

confidence: 82%

Electronic properties across metal-insulator transition in β -pyrochlore-type CsW2O6 epitaxial films

Soma

Yoshimatsu

Horiba

et al. 2018

Phys. Rev. Materials

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“…While significant experimental progress has recently been made in bulk A-227 compounds, 5, including the demonstration of all-in/all-out non-collinear magnetic order, 24,38 observation of giant magnetoresistance associated with metallic domain walls [34][35][36] and indication of Weyl semimetal phases, 18,37 there are only a few studies on thin film samples, [39][40][41][42][43] which is largely due to the great challenges in obtaining high quality films. Theoretical studies on pyrocholore iridate thin films have suggested a variety of emergent topological properties, including the quantized anomalous Hall conductance 44 and the correlated Chern insulator 45 that are otherwise not accessible in bulk samples.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial thin films of pyrochlore iridate Bi2+xIr2-yO7-δ: structure, defects and transport properties

Yang

Xie

Zhu

et al. 2017

Sci Rep

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While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. Here we report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi2Ir2O7. The films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of BiIr antisite defects, qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.

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“…These proposed heterostructures can be realized using modern thin film growth techniques such as molecular beam epitaxy or pulsed laser deposition, owing to the stable +4 valence of Ir and Ti, as demonstrated by the recent successful growth of the spin ice and the iridate thin films [26][27][28][29] . While the lattice mismatch between bulk spin ice and iridate compounds is comparatively small (1%), even a modest epitaxial strain can lift frustration in the spin ice layer 26 .…”

Section: Discussionmentioning

confidence: 99%

Two-dimensional magnetic monopole gas in an oxide heterostructure

et al. 2020

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Magnetic monopoles have been proposed as emergent quasiparticles in pyrochlore spin ice compounds. However, unlike semiconductors and two-dimensional electron gases where the charge degree of freedom can be actively controlled by chemical doping, interface modulation, and electrostatic gating, there is as of yet no analogue of these effects for emergent magnetic monopoles. To date, all experimental investigations have been limited to large ensembles comprised of equal numbers of monopoles and antimonopoles in bulk crystals. To address these issues, we propose the formation of a two-dimensional magnetic monopole gas (2DMG) with a net magnetic charge, confined at the interface between a spin ice and an isostructural antiferromagnetic pyrochlore iridate and whose monopole density can be controlled by an external field. Our proposal is based on Monte Carlo simulations of the thermodynamic and transport properties. This proposed 2DMG should enable experiments and devices which can be performed on magnetic monopoles, akin to two-dimensional electron gases in semiconductor heterostructures.

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Epitaxial growth of iridate pyrochlore Nd2Ir2O7 films

Cited by 35 publications

References 24 publications

Electronic properties across metal-insulator transition in β -pyrochlore-type CsW2O6 epitaxial films

Electronic properties across metal-insulator transition in β -pyrochlore-type CsW2O6 epitaxial films

Epitaxial thin films of pyrochlore iridate Bi2+xIr2-yO7-δ: structure, defects and transport properties

Two-dimensional magnetic monopole gas in an oxide heterostructure

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