Structural transition and anisotropic magnetism in disordered Zintl phase Eu7Ga6Sb8

Single crystals of the Zintl compound Eu7Ga6Sb8 were synthesized using a Ga-Sb flux. We report the temperature (T) and magnetic field (H) dependence of the magnetic susceptibility (χ), magnetization (M), resistivity (ρ), specific heat (C), and thermal expansion (α). We also report high-resolution powder x-ray diffraction data that support a structural phase transition with accompanying signatures seen in C(T), ρ(T), and α(T). We find Eu7Ga6Sb8 exhibits antiferromagnetic ordering at TN1=9.0 K from anomalies seen in χ(T), C(T), and α(T), as well as a potential reorientation of Eu2+ spins at TN2=7.5 K and TN3=7.2 K. Density functional theory calculations predict Eu7Ga6Sb8 to be semiconducting; however, electrical resistivity measurements show bad-metal behavior that indicates the presence of disorder.