PREPARATION, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF THE INTERMETALLIC COMPOUNDS LN(7-DR, LU)(X)RE(12)AL(61+Y) (LN=Y, GD)

The compounds Ln(7+x)Re(12)Al(61+y) (Ln=Gd, Tb, Dy, Lu) have been prep ared for the first time. They crystallize with the hexagonal Y7.28Re12 Al61.38 type structure (P6(3)/mcm, Z=1), which was refined for three r epresentatives from single-crystal X-ray data to residuals of less tha n 2%, yielding the compositions Gd7.23Re12Al61.70, Dy7.50Re12Al61.02 a nd Lu7.61Re12Al61.02. The differences in the compositions result from the variable occupancy of three crystallographic sites located on the hexagonal axis at 0, 0, z. The compositions correlate with the atomic size of the rare earth components. The magnetic properties of several compounds have been determined with a SQUID magnetometer in the temper ature range from 2 to 300 K with magnetic flux densities up to 5.5 T.Y 7.28Re12Al61.38 is Pauli paramagnetic, indicating that the rhenium ato ms in these isotypic compounds do not carry magnetic moments. The beha viour of the other compounds is dominated by the magnetic properties o f the rare earth components. Gd7.23Re12Al61.70 is antiferromagnetic. T he terbium compound is metamagnetic. Dy7.50Re12Al61.17 and the earlier reported compounds Ho7.32Re12Al61.48 and Er7+xRe12Al61+y are ferromag netic. The magnetic ordering temperatures are all lower than 15 K. (C) 1997 Elsevier Science S.A.