Magnetic Moment Fragmentation in an All-in-All-out Pyrochlore $\mathrm{Nd_2Sn_2O_7}$
Authors
Yi Luo
Matthew Powell
Joseph A. M. Paddison
Brenden R. Ortiz
J. Ross Stewart
Joseph W. Kolis
Adam A. Aczel
Abstract
We report single crystal neutron spectroscopy and bulk characterization on hydrothermally grown $\mathrm{Nd_2Sn_2O_7}$, revealing magnetic moment fragmentation embedded within the all-in-all-out ordered state. The spectra show a nearly flat band with pinch-point-like momentum dependence, accompanied by dispersive branches that generate half-moon features across multiple Brillouin zones. These defining signatures are captured quantitatively by a minimal dipolar-octupolar spin Hamiltonian, demonstrating excellent agreement between experiment and theory. The higher flat-mode energy helps account for the absence of dynamical interference in prior $\mathrm{μSR}$ studies, while the lack of any photon-like excitation imposes strict constraints on the proposed Coulombic antiferromagnet scenario. Our results extend moment fragmentation to $\mathrm{Nd_2Sn_2O_7}$ and identify it as a clean, tractable platform for quantitative exploration of emergent gauge field physics and multipolar spin-wave dynamics in frustrated magnets.
