Nd2Sn2O7: an all-in-all-out pyrochlore magnet with no divergence-free field and anomalously slow paramagnetic spin dynamics

TL;DR

This study investigates Nd2Sn2O7, revealing a noncoplanar magnetic order, unusual slow spin dynamics, and the absence of divergence-free fields, providing insights into pyrochlore magnet behavior.

Contribution

It presents the first detailed measurements of Nd2Sn2O7's magnetic transition, spin dynamics, and field properties, highlighting novel slow paramagnetic dynamics and the absence of divergence-free fields in this material.

Findings

Magnetic transition at ~0.91 K to all-in-all-out order

Slow paramagnetic spin dynamics up to ~30 Tc

Absence of divergence-free field in ground state

Abstract

We report measurements performed on a polycrystalline sample of the pyrochlore compound Nd2Sn2O7. It undergoes a second order magnetic phase transition at Tc ~ 0.91 K to a noncoplanar all-in-all-out magnetic structure of the Nd3+ magnetic moments. The thermal behavior of the low temperature specific heat fingerprints excitations with linear dispersion in a three-dimensional lattice. The temperature independent spin-lattice relaxation rate measured below Tc and the anomalously slow paramagnetic spin dynamics detected up to ~ 30 Tc are suggested to be due to magnetic short-range correlations in unidimensional spin clusters, i.e., spin loops. The observation of a spontaneous field in muon spin relaxation measurements is associated with the absence of a divergence-free field for the ground state of an all-in-all-out pyrochlore magnet as predicted recently.