Beyond Magnons in Nd2ScNbO7: An Ising Pyrochlore Antiferromagnet with All-in-All-Out Order and Random Fields

Published

October 20, 2021

Author(s)

A. Scheie, M. Sanders, Xin Gui, Yiming Qiu, Timothy R. Prisk, R. J. Cava, Collin L. Broholm

Abstract

We report the low temperature magnetic properties of Nd³⁺ pyrochlore Nd₂ScNbO₇. Susceptibility and magnetization show an easy-axis moment, and heat capacity reveals a phase transition to long range order at T_N = 370 mK with a fully recovered Δ}S = Rln(2), 53% of it recovered for T > TN. Elastic neutron scattering shows a long-range ordered all-in-all-out magnetic ordered structure with low-Q diffuse elastic scattering. Inelastic neutron scattering shows a low-energy flat-band,indicating a magnetic Hamiltonian similar to Nd₂Zr₂O₇. Nuclear hyperfine excitations measured by ultra-high-resolution neutron backscattering indicates a distribution of static electronic moments below TN, 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 Nd₂Zr₂O₇. Comparing local static moments also reveals a suppression of the nuclear Schottky anomaly in temperature, evidencing strong low-T quantum fluctuations in the electronic moments. Taken together, these measurements indicate an unusual fluctuating magnetic ground state. Such observations in Nd₂ScNbO₇ and Nd₂Zr₂O₇ are consistent with exotic spinons of a proximate quantum spin liquid or disorder-induced local spin excitations.

Citation

Physical Review B

Volume

104

Issue

13

Pub Type

Journals

Keywords

Ising pyrochlore antiferromagnet, neutron scattering

Citation

Scheie, A. , Sanders, M. , Gui, X. , Qiu, Y. , Prisk, T. , Cava, R. and Broholm, C. (2021), Beyond Magnons in Nd₂ScNbO₇: An Ising Pyrochlore Antiferromagnet with All-in-All-Out Order and Random Fields, Physical Review B (Accessed April 26, 2024)