Flux Crystal Growth of the RE2Ru3Ge5 (RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions

Previously synthesized only as powders, single crystals of the RE₂Ru₃Ge₅ (RE = La, Ce, Nd, Gd, Tb) series of compounds have now been obtained from molten In. These materials crystallize with the U₂Co₃Si₅-type structure in orthorhombic space group Ibam with lattice parameters a ≈ 10.00-9.77 Å (La-Tb), b ≈ 12.51-12.35 Å, and c ≈ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe₅ and RuGe₆ units, as well as Ge-Ge zigzag chains. This structure type and those of the other five (Sc₂Fe₃Si₅, Lu₂Co₃Si₅, Y₂Rh₃Sn₅, Yb₂Ir₃Ge₅, and Yb₂Pt₃Sn₅) to compose the RE₂T₃X₅ phase space are discussed in depth. For the three compounds with RE = Nd, Gd, Tb, multiple magnetic transitions and metamagnetic behavior are observed. Electronic band structure calculations performed on La₂Ru₃Ge₅ indicate that these materials have a negative band gap and are semimetallic in nature.