The monoclinic superstructure of the M ₂Pt₆Al₁₅ series (M=Ca, Sc, Y, La, Lu)

Abstract

The five ternary intermetallic compounds

Magnetic Properties of theRE2Pt6X15(RE= Y, La–Nd, Sm, Gd–Lu;X= Al, Ga) Series

“…The RE 2 Pt 6 X 15 ( X = Al, Ga) compounds all crystallize as a monoclinic superstructure of the hexagonal RE 0.67 Pt 2 Al 5 (≡ RE 2 Pt 6 Al 15 ) series ( RE = Y, Gd–Tm; P 6 3 / mmc ) described in the literature. Recently, we reported on the crystal structure of Sc 2 Pt 6 Al 15 . The hexagonal subcell is readily found by standard indexing routines, however, additional reflections are evident in the hk 0 planes from the reconstructed diffraction patterns in single crystals obtained using our synthetic conditions.…”

“…Unit cell parameters a and c and unit cell volume V of the hexagonal subcell of the ( top ) RE 2 Pt 6 Al 15 ( RE = Y, Ce–Nd, Sm, Gd–Lu) and ( bottom ) RE 2 Pt 6 Ga 15 ( RE = Y, La–Nd, Sm, Gd–Lu) series. The lattice parameters of Y 2 Pt 6 Al 15 , La 2 Pt 6 Al 15 and Lu 2 Pt 6 Al 15 as well as Eu 2 Pt 6 Al 15 and Eu 2 Pt 6 Ga 15 are taken from the literature. A comparison with all other reported unit cell parameters is given in Table 1.…”

“…As the crystal structure of the RE 2 Pt 6 Al 15 series has been described in detail before, we will only briefly review the important structural features. The structure is comprised of two [Pt 3 Al 6 ] building blocks A and A' (Figure ), which get stacked along the crystallographic b axis in a ··· ABA'B' ··· sequence.…”

“…The rare‐earth atoms are surrounded by six Pt (337–338 pm) and eleven Al atoms (304–335 pm) in the shape of a distorted fivefold capped hexagonal prism. Additional details regarding the structure description can be found in the literature …”

“…Although these compounds have been known for quite some time, not all of their physical properties have been investigated in detail. Sc 2 Pt 6 Al 15 , Y 2 Pt 6 Al 15 , La 2 Pt 6 Al 15 and Lu 2 Pt 6 Al 15 as well as Ca 2 Pt 6 Al 15 were reported to be Pauli‐paramagnetic materials, however, in some cases the intrinsic diamagnetism overcompensated the conduction electron contributions . No superconductivity was observed for these samples.…”