Superexchange coupling between a dilute Gd3+ probe and orphan spins in a valence-bond glass
Abstract
The valence-bond-glass state of the 4d^1 double perovskite Ba2YMoO6 combines Mo^5+ singlets with residual paramagnetic "orphan" spins whose coupling is hard to reach with bulk probes. We probe them by electron paramagnetic resonance of a dilute Gd^3+ ion on the Y^3+ site via broadband coplanar-waveguide transmission at 5 K. The isostructural nonmagnetic niobate Ba2YNbO6, doped with the same Gd^3+ probe, is a fixed-lattice control. The Gd^3+ linewidth nearly doubles in the magnetic host. Dipolar coupling to the sparse orphans is nearly an order of magnitude too weak; the excess is instead reproduced by a transferred f-d superexchange of J ~ 0.2 K, so the width is a static measure of orphan-spin coupling. The half-field (Delta m_S = +/-2) satellite collapses in the magnetic host, a dynamical dephasing channel, while the unchanged g-factor marks a zero-mean random internal field. Together the two channels probe the coupling and dynamics of valence-bond-glass orphan spins.
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BibTeX
@misc{colgan2026superexchange,
title = {{Superexchange coupling between a dilute Gd3+ probe and orphan spins in a valence-bond glass}},
author = {Patrick Colgan and Artur Solodovnyk and Jeremy P. Carlo and Scott Dietrich},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18722},
eprint = {2610.18722},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18722},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Superexchange coupling between a dilute Gd3+ probe and orphan spins in a valence-bond glass
AU - Patrick Colgan
AU - Artur Solodovnyk
AU - Jeremy P. Carlo
AU - Scott Dietrich
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18722
UR - https://arxiv.org/abs/2610.18722
AB - The valence-bond-glass state of the 4d^1 double perovskite Ba2YMoO6 combines Mo^5+ singlets with residual paramagnetic "orphan" spins whose coupling is hard to reach with bulk probes. We probe them by electron paramagnetic resonance of a dilute Gd^3+ ion on the Y^3+ site via broadband coplanar-waveguide transmission at 5 K. The isostructural nonmagnetic niobate Ba2YNbO6, doped with the same Gd^3+ probe, is a fixed-lattice control. The Gd^3+ linewidth nearly doubles in the magnetic host. Dipolar coupling to the sparse orphans is nearly an order of magnitude too weak; the excess is instead reproduced by a transferred f-d superexchange of J ~ 0.2 K, so the width is a static measure of orphan-spin coupling. The half-field (Delta m_S = +/-2) satellite collapses in the magnetic host, a dynamical dephasing channel, while the unchanged g-factor marks a zero-mean random internal field. Together the two channels probe the coupling and dynamics of valence-bond-glass orphan spins.
ER -