Colossal Magnetoresistance and Phonon Driven Exchange Dynamics in Eu$_5$Sn$_2$As$_6$
Luke Pritchard Cairns, Kohtaro Yamakawa, Shengzhi Zhang, Youzhe Chen, Bernard Field + 7 more
TLDR
This paper investigates colossal magnetoresistance in Eu$_5$Sn$_2$As$_6$, revealing how phonon dynamics and lattice interactions drive electron delocalization.
Key contributions
- Measured thermal conductivity and magnetostriction in Eu$_5$Sn$_2$As$_6$.
- Observed strong field-dependence in both properties, mirroring magnetization saturation.
- Interpreted enhanced phonon thermal conductivity via lifting spin configuration degeneracy.
- Proposed suppressed phonon scattering from exchange frustration drives electron delocalization.
Why it matters
This study sheds light on the mechanism of colossal magnetoresistance in a new class of Eu-based antiferromagnets. It highlights the critical role of crystal lattice and phonon dynamics in driving electron delocalization, offering a fresh perspective beyond traditional models.
Original Abstract
The emergence of colossal magnetoresistance in a new generation of Eu$^{2+}$-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 Eu$_5$Sn$_2$As$_6$ -- 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 Eu$^{2+}$ 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.
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