Unusual magnetic and transport properties in the Zintl phase Eu$_{11}$Zn$_6$As$_{12}$

TL;DR

This study reports the synthesis and detailed investigation of Eu$_{11}$Zn$_6$As$_{12}$, revealing complex magnetic transitions, strong ferromagnetic fluctuations, metallic conductivity, and magnetoresistance effects, highlighting the rich physics of Eu-based Zintl phases.

Contribution

The paper introduces a new Eu-containing Zintl phase with unique magnetic and transport properties, expanding understanding of Eu-based Zintl compounds.

Findings

Two magnetic transitions at 22 K and 9 K

Strong ferromagnetic fluctuations around 29 K

Metallic behavior with negative magnetoresistance

Abstract

Narrow-gap rare-earth Zintl phases frequently exhibit fascinating physical phenomena due to their various crystal structures, complex magnetic properties, and tunable transport behaviors. Here we report the synthesis, magnetic, thermodynamic, and transport properties of a Eu-containing Zintl arsenide, Eu$_{11}$Zn$_6$As$_{12}$, which consists of infinite chains of Eu cations and anionic frameworks constructed from corner-sharing ZnAs$_4$ tetrahedra. Eu$_{11}$Zn$_6$As$_{12}$ exhibits complicated magnetic behavior owing to intricate exchange interactions mediated by the discrete anionic fragments. Two long-range magnetic transitions at 22 K ($T_\mathrm{N}$) and 9 K ($T^*$), as well as exceptionally strong ferromagnetic fluctuations around 29 K ($T_\mathrm{F}$), are indicated by the susceptibility, heat capacity and resistivity measurements. Besides, Eu$_{11}$Zn$_6$As$_{12}$ displays metallic behavior, attributable to the hole carriers doped by slight Eu vacancies or the mixed valence of Eu$^{2+}$ and Eu$^{3+}$. A prominent resistivity peak occurs around $T_\mathrm{N}$, which is rapidly suppressed by the applied field, leading to a prominent negative magnetoresistance effect. A resistivity hysteresis is observed below 5 K, caused by a small net ferromagnetic component. Our study presents the distinct magnetic and transport properties of Eu$_{11}$Zn$_6$As$_{12}$, and further experiments are required to elucidate the origin of these novel behaviors. Moreover, our findings demonstrate that Eu-based Zintl phases are a fertile ground to study the interplay between magnetism and charge transport.