Metal flux crystal growth technique in the determination of ordered superstructure in EuInGe

Abstract

High quality single crystals of EuInGe were grown from the reaction run with excess indium. X-ray diffraction investigations showed that EuInGe crystallizes with a pronounced subcell structure, superstructure of the ThSi2 type: Pnma space group, a = 4.9066(10) Å, b = 3.9834(8) Å and c = 15.964(3) Å. However, the powder X-ray pattern reveals weak superstructure reflections, and the inclusion of additional reflections in the analysis points to a new type of structural arrangement, in a monoclinic system, P21/c space group, a = 7.9663(16) Å, b = 4.9119(10) Å, c = 16.465(5) Å, and β = 104.03. Magnetization measurements carried out as a function of temperature show multiple magnetic transitions at 13, 25, 44, and 70 K. In the temperature region above 100 K, the Curie-Weiss law is followed indicating a paramagnetic state of the sample. Magnetic moments deduced from this region suggest europium to be in a divalent state, which was further confirmed by 151Eu Mössbauer spectroscopic measurements. Experiments were accompanied by first-principles density functional calculations using the full-potential linear muffin-tin orbital method within the local density approximation (LSDA) and including the onsite Coulomb interaction (LSDA+U) for the Eu-f states. The density of states shows a pronounced pseudo gap feature around the Fermi level. The inclusion of a Hubbard U has only a minor effect on the band structure. From the calculated total energies the P21/c structure is favorable by 25 meV per formula unit when compared to the Pnma subcell structure. © 2012 American Chemical Society.