Colossal magnetoresistance (CMR) has been observed across many Eu2+-based materials; however, its origin is not completely understood. Here we investigate the antiferromagnetic insulator EuZn2P2 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 TN=23K. Dilatometry measurements show an accompanying field-induced lattice strain. Additionally, Eu2+ electron spin resonance reveals a strong ferromagnetic exchange interaction between Eu2+ and conduction electrons. Our experimental results in EuZn2P2 are consistent with a magnetic polaron scenario and suggest magnetic polaron formation as a prevailing explanation of CMR in Eu2+-based compounds.
@article{arxiv.2504.05494,
title = {Magnetic polaron formation in EuZn$_2$P$_2$},
author = {Matthew S. Cook and Elizabeth A. Peterson and Caitlin S. Kengle and E. R. Kennedy and J. Sheeran and Clément Girod and G. S. Freitas and Samuel M. Greer and Peter Abbamonte and P. G. Pagliuso and J. D. Thompson and Sean M. Thomas and P. F. S. Rosa},
journal= {arXiv preprint arXiv:2504.05494},
year = {2025}
}