Colossal magnetoresistance in antiferromagnetic EuZn₂P₂

Matthew S. Cook, Clément Girod, Sean M. Thomas, Daniele S. M. Alves, Joe Thompson and, Priscila F. S. Rosa

Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

EuZn₂P₂ is a Zintl phase with proposed A-type antiferromagnetic ordering of Eu²⁺ moments with T_n = 23 K [1]. In contrast to the predicted topological semimetal state in EuCd₂As₂, EuZn₂P₂ is experimentally found to be a narrow-gap semiconductor. The bandgap has been previously estimated to be 110 meV from electrical transport measurements, which is smaller than that calculated from first principles (480 meV). As this material is remarkably insulating at low temperatures, electrical transport measurements have only been reported to 150 K and in zero magnetic field. Here we present electrical resistivity measurements to 10 K in fields to 9 T. We find large negative magnetoresistance (MR% = 100% x (R(H)-R(0))/R(0)) which reaches -99.94% near T_n and remains large well above and below the ordering temperature. Low temperature Arrhenius fits to the electrical resistivity yield a bandgap of approximately 10 meV in the ordered state. We also report dilatometry measurements to track the anisotropy of magnetic ordering in this material and to estimate the pressure dependence of T_n. We discuss the potential mechanisms behind the large negative MR in EuZn₂P₂ and how the transport properties relate to other Eu based systems that show colossal magnetoresistance [2,3].

[1] Berry, Tanya, Veronica J. Stewart, Benjamin W. Y. Redemann, Chris Lygouras, Nicodemos Varnava, David Vanderbilt, and Tyrel M. McQueen. Physical Review B 106, no. 5 (August 17, 2022): 054420.

[2] Blawat, Joanna, Madalynn Marshall, John Singleton, Erxi Feng, Huibo Cao, Weiwei Xie, and Rongying Jin. Advanced Quantum Technologies 5, no. 6 (June 2022): 2200012.

[3] Wang, Zhi-Cheng, Jared D. Rogers, Xiaohan Yao, Renee Nichols, Kemal Atay, Bochao Xu, Jacob Franklin, et al. Advanced Materials 33, no. 10 (March 2021): 2005755.