Unusual magnetic and transport properties in the Zintl phase Eu11Zn6As12

Narrow-gap rare-earth Zintl phases frequently exhibit fascinating physical phenomena owing 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, ${\mathrm{Eu}}_{11}{\mathrm{Zn}}_{6}{\mathrm{As}}_{12}$, which consists of infinite chains of Eu cations and anionic frameworks constructed from corner-sharing ${\mathrm{ZnAs}}_{4}$ tetrahedra. ${\mathrm{Eu}}_{11}{\mathrm{Zn}}_{6}{\mathrm{As}}_{12}$ 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, ${\mathrm{Eu}}_{11}{\mathrm{Zn}}_{6}{\mathrm{As}}_{12}$ displays metallic behavior, attributable to the hole carriers doped by slight Eu vacancies or the mixed valence of ${\mathrm{Eu}}^{2+}$ and ${\mathrm{Eu}}^{3+}$. A prominent resistivity peak occurs around ${T}_{\mathrm{N}}$, which is rapidly suppressed by the applied field, leading to a large 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 ${\mathrm{Eu}}_{11}{\mathrm{Zn}}_{6}{\mathrm{As}}_{12}$, and further experiments are required to elucidate the origin of these behaviors. Moreover, our findings demonstrate that Eu-based Zintl phases are a fertile ground to study the interplay between magnetism and charge transport.