Magnetic polaron formation in EuZn$_2$P$_2$

Matthew S. Cook; Elizabeth A. Peterson; Caitlin S. Kengle; E. R. Kennedy; J. Sheeran; Clément Girod; G. S. Freitas; Samuel M. Greer; Peter Abbamonte; P. G. Pagliuso; J. D. Thompson; Sean M. Thomas; P. F. S. Rosa

arXiv · 2504.05494

Magnetic polaron formation in EuZn$_2$P$_2$

Matthew S. Cook·Elizabeth A. Peterson·Caitlin S. Kengle·E. R. Kennedy·J. Sheeran·Clément Girod·G. S. Freitas·Samuel M. Greer·Peter Abbamonte·P. G. Pagliuso·J. D. Thompson·Sean M. Thomas·P. F. S. Rosa

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Abstract

Colossal magnetoresistance (CMR) has been observed across many Eu$^{2+}$-based materials; however, its origin is not completely understood. Here we investigate the antiferromagnetic insulator EuZn$_2$P$_2$ through single crystal x-ray diffraction, transmission electron microscopy, electrical transport, magnetization, dilatometry, and electron spin resonance measurements complemented by density functional theory calculations. Our electrical resistivity data reveal a large negative magnetoresistance, $MR = [R(H)-R(0)]/R(0)$, that reaches $MR = -99.7\%$ at 9~T near the antiferromagnetic ordering temperature $T_N=23\ \text{K}$. Dilatometry measurements show an accompanying field-induced lattice strain. Additionally, Eu$^{2+}$ electron spin resonance reveals a strong ferromagnetic exchange interaction between Eu$^{2+}$ and conduction electrons. Our experimental results in EuZn$_2$P$_2$ are consistent with a magnetic polaron scenario and suggest magnetic polaron formation as a prevailing explanation of CMR in Eu$^{2+}$-based compounds.

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Matthew S. Cook, Elizabeth A. Peterson, Caitlin S. Kengle, E. R. Kennedy, J. Sheeran, Clément Girod, G. S. Freitas, Samuel M. Greer, Peter Abbamonte, P. G. Pagliuso, J. D. Thompson, Sean M. Thomas, P. F. S. Rosa. 2025-04-07. Magnetic polaron formation in EuZn$_2$P$_2$. https://arxiv.org/abs/2504.05494

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