Eu₄Bi₃: Crystal structure, magnetic and electronic properties

The Eu-Bi system contains the phases Eu₅Bi₃, Eu₄Bi₃ and Eu₁₁B₁₀. The structure types of these phases have been determined by powder X-ray diffraction. Crystals of Eu₄Bi₃ (cubic, space group I43d; a = 9.920 Å, Z = 4, T = 130 K, R1/wR2 = 4.86/10.84%) were obtained in low yield by reaction of Eu, Mn, and Bi in the ratio 14:1:11 in a closed niobium tube (heating rate 30°C/h; reaction at 1050°C for 300 h, cooling rate 100°C/h). The crystal structure consists of distorted octahedra made up of six Bi coordinated to a central Eu atom. Eu is also coordinated to three other Eu atoms and forms a three-dimensional network composed of interconnected rings. The Bi atoms are coordinated to eight Eu atoms. High yields of Eu₄Bi₃ can be prepared by reacting stoichiometric amount of the elements in a sealed tantalum tube at 1100°C for 24 h. Temperature dependent magnetic susceptibility is consistent with antiferromagnetic behavior with an ordering temperature of 18 K. The data could be fit with the Curie-Weiss law and a moment of 7.38 μ_B/Eu is obtained, consistent with all Eu atoms being Eu^II. Temperature dependent resistivity indicates that Eu₄Bi₃ is a metal with a room temperature resistance of 1.3 Ωcm.