Beyond magnons in Nd2ScNbO7: An Ising pyrochlore antiferromagnet with all in all out order and random fields

Abstract

We report the low temperature magnetic properties of Nd${}^{3+}$ pyrochlore $\mathrm{N}{\mathrm{d}}_2\mathrm{ScNb}{\mathrm{O}}_7$. Susceptibility and magnetization show an easy-axis moment, and heat capacity reveals a phase transition to long range order at $T_N=371(2)$ mK with a fully recovered $\Delta S=R\ln (2)$, 53\% of it recovered for $T>T_N$. Elastic neutron scattering shows a long-range all-in-all-out magnetic order with low-$Q$ diffuse elastic scattering. Inelastic neutron scattering shows a low-energy flat-band, indicating a magnetic Hamiltonian similar to $\mathrm{N}{\mathrm{d}}_2\mathrm{Z}{\mathrm{r}}_2{\mathrm{O}}_7$. Nuclear hyperfine excitations measured by ultra-high-resolution neutron backscattering indicates a distribution of static electronic moments below $T_N$, which may be due to B-site disorder influencing Nd crystal electric fields. Analysis of heat capacity data shows an unexpected $T$-linear or $T^{3/2}$ term which is inconsistent with conventional magnon quasiparticles, but is consistent with fractionalized spinons or gapless local spin excitations. We use legacy data to show similar behavior in $\mathrm{N}{\mathrm{d}}_2\mathrm{Z}{\mathrm{r}}_2{\mathrm{O}}_7$. Comparing local static moments also reveals a suppression of the nuclear Schottky anomaly in temperature, evidencing a fraction of Nd sites with nearly zero static moment, consistent with exchange-disorder-induced random singlet formation. Taken together, these measurements suggest an unusual fluctuating magnetic ground state which mimics a spin-liquid -- but may not actually be one.

Main text: 11 pages, 9 figures. Appendices: 6 pages and 7 figures

References in corpus (14)

• Pyrochlore Photons: The U(1) Spin Liquid in a S=1/2 Three-Dimensional Frustrated Magnet
• Quantum Spin Ice Dynamics in the Dipole-Octupole Pyrochlore Magnet Ce${}_2$Zr${}_2$O${}_7$
• Impact of Stoichiometry of Yb2Ti2O7 on its Physical Properties
• Structural and Magnetic Investigations of Single-Crystals of the Neodymium Zirconate Pyrochlore, Nd2Zr2O7
• Direct determination of the spin structure of Nd${}_2$Ir${}_2$O${}_7$ by means of neutron diffraction
• Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements
• Fragmentation in Frustrated Magnets -- A review
• Low temperature specific heat and possible gap to magnetic excitations in the Heisenberg pyrochlore antiferromagnet Gd2Sn207
• Fragmented monopole crystal, dimer entropy and Coulomb interactions in Dy${}_2$Ir${}_2$O${}_7$
• Spin dynamics of the ordered dipolar-octupolar pseudospin-${}^1{/}_2$ pyrochlore Nd${}_2$Zr${}_2$O${}_7$ probed by muon spin relaxation
• Synthesis and structure of new pyrochlore-type oxides Ln2ScNbO7 (Ln = Pr, Nd, Eu, Gd, Dy)
• Muon spin relaxation and inelastic neutron scattering investigations of all-in/all-out antiferromagnet Nd2Hf2O7
• Anisotropic exchange Hamiltonian, magnetic phase diagram and domain inversion of Nd${}_2$Zr${}_2$O${}_7$
• Homogenous reduced moment in a gapful scalar chiral kagome antiferromagnet

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• Impact of disorder in Nd-based pyrochlore magnets
• Hidden frustration in the triangular-lattice antiferromagnet NdCd3P3
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