The emergence of colossal magnetoresistance in a new generation of Eu2+-based antiferromagnets is intriguing given stark contrasts to the archetypal perovskite manganites and doped Eu-chalcogenides. In this study the thermal conductivity and magnetostriction of Eu5Sn2As6 -- one such representative -- have been measured to better understand the role of the crystal lattice. Both properties are strongly field-dependent and mirror the magnetization, saturating once the Eu2+ moments are polarized. The field-enhancement of the phonon-dominated thermal conductivity is interpreted through the lifting of a degeneracy of spin configurations, and the subsequent saturation due to quenched magnetostrain in high field. Comparison with spin-glass insulators suggests that this phenomenon is not a byproduct but rather the driver of electron delocalization due to the suppression of strong phonon scattering arising from exchange frustration.
@article{arxiv.2605.06649,
title = {Colossal Magnetoresistance and Phonon Driven Exchange Dynamics in Eu$_5$Sn$_2$As$_6$},
author = {Luke Pritchard Cairns and Kohtaro Yamakawa and Shengzhi Zhang and Youzhe Chen and Bernard Field and Rainer Reczek and Ryan P. Day and Joel E. Moore and Marcelo Jaime and Sinead M. Griffin and Robert J. Birgeneau and James G. Analytis},
journal= {arXiv preprint arXiv:2605.06649},
year = {2026}
}