Carrier-induced transition from antiferromagnetic insulator to ferromagnetic metal in the layered phosphide EuZn$_2$P$_2$

TL;DR

This study demonstrates that hole carriers induced by Eu vacancies in EuZn₂P₂ transform it from an antiferromagnetic insulator to a ferromagnetic metal with tunable magnetic and transport properties, promising for spintronics.

Contribution

The paper reports the synthesis of EuZn₂P₂ with metallic and ferromagnetic properties, revealing carrier-induced magnetic transition and tunable charge transport in Eu$M_2X_2$ compounds.

Findings

EuZn₂P₂ exhibits metallic behavior and ferromagnetism at 72 K.

Hole carriers from Eu vacancies are crucial for magnetic and transport changes.

Negative magnetoresistance near T_C is observed and explained by the Majumdar-Littlewood model.

Abstract

EuZn$_2$P$_2$ was reported to be an insulating antiferromagnet with $T_\mathrm{N}$ of 23.5 K. In this study, single crystals of EuZn$_2$P$_2$ exhibiting metallic behavior and a ferromagnetic order of 72 K ($T_\mathrm{C}$) are successfully synthesized via a salt flux method. The presence of hole carriers induced by the Eu vacancies in the lattice is found to be crucial for the drastic changes in magnetism and electrical transport. The carriers mediate the interlayer ferromagnetic interaction, and the coupling strength is directly related to $T_\mathrm{C}$, as evidenced by the linear dependence of $T_\mathrm{C}$ and the fitted Curie-Weiss temperatures on the Eu-layer distances for ferromagnetic Eu$M_2X_2$ ($M$ = Zn, Cd; $X$ = P, As). The ferromagnetic EuZn$_2$P$_2$ shows conspicuous negative magnetoresistance (MR) near $T_\mathrm{C}$, owing to strong magnetic scattering. The MR behavior is consistent with the Majumdar-Littlewood model, indicating that the MR can be enhanced by decreasing the carrier density. Our findings suggest that Eu$M_2X_2$ has highly tunable magnetism and charge transport, making it a promising material family for potential applications in spintronics.