Antiferromagnetic transition in ${\text{EuFe}}_2{\text{As}}_2$: A possible parent compound for superconductors

Ternary iron arsenide ${\text{EuFe}}_2{\text{As}}_2$ with ${\text{ThCr}}_2{\text{Si}}_2$-type structure has been studied by magnetic susceptibility, resistivity, thermopower, Hall, and specific-heat measurements. The compound undergoes two magnetic phase transitions at about 200 and 20 K, respectively. The former was found to be accompanied with a slight drop in magnetic susceptibility (after subtracting the Curie-Weiss paramagnetic contribution), a rapid decrease in resistivity, a large jump in thermopower, and a sharp peak in specific heat with decreasing temperature, all of which point to a spin-density-wave-like antiferromagnetic transition. The latter was proposed to be associated with an $A$-type antiferromagnetic ordering of ${\text{Eu}}^{2+}$ moments. Comparing with the physical properties of the isostructural compounds ${\text{BaFe}}_2{\text{As}}_2$ and ${\text{SrFe}}_2{\text{As}}_2$, we expect that superconductivity could be induced in ${\text{EuFe}}_2{\text{As}}_2$ through appropriate doping.

Figure 1

(Color online) X-ray powder-diffraction pattern at room temperature for the ${\text{EuFe}}_2{\text{As}}_2$ sample. A small amount of FeAs impurity was identified. The inset shows schematic crystal structure of ${\text{EuFe}}_2{\text{As}}_2$.

Figure 2

(Color online) (a) Temperature dependence of magnetic susceptibility for the ${\text{EuFe}}_2{\text{As}}_2$ sample. The inset shows a drop in $\chi$ at $T^{\ast }=200\text{K}$ after subtraction of the Curie-Weiss contribution of ${\text{Eu}}^{2+}$ moments. The red lines are the guide to the eyes. (b) Field dependence of magnetization at low temperatures for the ${\text{EuFe}}_2{\text{As}}_2$ sample.

Figure 3

(Color online) Temperature dependences of (a) resistivity, (b) thermopower, and (c) Hall coefficient for the ${\text{EuFe}}_2{\text{As}}_2$ sample. The inset of (a) is an expanded plot for showing low-temperature data.

Figure 4

(Color online) Temperature dependence of specific heat for the ${\text{EuFe}}_2{\text{As}}_2$ sample. The inset is an expanded plot, showing no detectable thermal hysteresis around 200 K.