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Description
EuZn$_{2}$P$_{2}$ is a narrow-gap semiconductor (0.11 eV) belonging to the Zintl phase family, characterized by mixed ionic and covalent bonding. Although long-range antiferromagnetic order is established only below $23$ K, strong short-range magnetic correlations significantly reduce electrical resistivity well above the ordering temperature, leading to a giant magnetoresistance effect.
The nature of magnetic interactions in EuZn$_{2}$P$_{2}$ remains under debate. We investigated the pressure dependence of the magnetic ordering temperature using DC magnetization measurements in a miniature diamond anvil cell made from nonmagnetic CuBe alloy. Our magnetization measurements reveal a linear increase in magnetization up to $\sim 4$ GPa, followed by a steeper linear rise up to 10 GPa, the limit of our experiment. Notably, no distinct anomaly in electrical resistivity accompanies magnetic ordering. The Néel temperature ($T_N$) at elevated pressures does not correlate with specific features in $R(T)$. Interestingly, the maximum in $R(T)$, although magnetism-related, appears at temperatures higher than the actual T$_N$ at corresponding pressures. We attribute this deviation from an exponentially increasing resistivity trend to magnetic fluctuations that induce the formation of magnetic polarons.
Hydrostatic pressure strongly enhances both the magnetic ordering temperature and the characteristic temperature of short-range magnetic correlations. As pressure increases, the band gap of EuZn$_{2}$P$_{2}$ gradually closes, and the material exhibits metallic-like behavior above $18$ GPa. The giant magnetoresistance effect remains significant even in this high-pressure metallic state and persists up to room temperature. The results suggest that above $18$ GPa, EuZn$_{2}$P$_{2}$ transitions into a ferromagnetically ordered metallic state.
Acknowledgements
The work has been supported by the Czech Science Foundation under the Grants No. 25-16339S. Experiments were performed in MGML (mgml.eu), which is supported within the program of the Czech Research Infrastructures (Project No. LM2023065).
