Magnetic fluctuations induced by geometric frustration of local Ir-spins disturb the formation of long-range magnetic order in the family of pyrochlore iridates. As a consequence, Pr2Ir2O7lies at a tuning-free antiferromagnetic-to-paramagnetic quantum critical point and exhibits an array of complex phenomena including the Kondo effect, biquadratic band structure, and metallic spin liquid. Using spectroscopic imaging with the scanning tunneling microscope, complemented with machine learning, density functional theory and theoretical modeling, we probe the local electronic states in Pr2Ir2O7and find an electronic phase separation. Nanoscale regions with a well-defined Kondo resonance are interweaved with a non-magnetic metallic phase with Kondo-destruction. These spatial nanoscale patterns display a fractal geometry with power-law behavior extended over two decades, consistent with being in proximity to a critical point. Our discovery reveals a nanoscale tuning route, viz. using a spatial variation of the electronic potential as a means of adjusting the balance between Kondo entanglement and geometric frustration.
Interplay between Kondo and magnetic interactions in Pr0.75Gd0.25ScGeH
Combined experimental and density functional theory (DFT) study of Pr0.75Gd0.25ScGe and its hydride
(Pr0.75Gd0.25ScGeH) reveals intricacies of composition-structure-property relationships in those distinctly layered
compounds. Hydrogenation of the intermetallic parent, crystalizing in a tetragonal CeScSi-type structure, leads to
an anisotropic volume expansion, that is, a(=b) lattice parameter decreases while the lattice expands along the c
direction, yielding a net increase of cell volume. DFT calculations predict an antiparallel coupling of localized Gd
and Pr magnetic moments in both materials at the ground state. While experiments corroborate this for the
parent compound, there is no conclusive experimental proof for the hydride, where Pr moments do not order
down to 3 K. DFT results also reveal that rare-earth – hydrogen interactions reduce spin-polarization of the Pr
and Gd 5d and Sc 3d states at the Fermi energy, disrupt indirect exchange interactions mediated by conduction
electrons, dramatically reduce the magnetic ordering temperature, and open a pseudo-gap in the majority-spin
channel. Both experiments and theory show evidence of Kondo-like behavior in the hydride in the absence of an
applied magnetic field, whereas increasing the field promotes magnetic ordering and suppresses Kondo-like
behavior.
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- Award ID(s):
- 1944551
- PAR ID:
- 10487536
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Alloys and Compounds
- Volume:
- 966
- Issue:
- C
- ISSN:
- 0925-8388
- Page Range / eLocation ID:
- 171351
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.jallcom.2023.171351
