ANTIFERROMAGNETIC ORDERING IN RPTSN (R=DY, HO, ER) COMPOUNDS

DyPtSn, HoPtSn and ErPtSn crystallize in the hexagonal Fe2P (ZrNiAl)-t ype structure and are antiferromagnetic below 9.5, 9.5 and 3.5 K, resp ectively. DyPtSn shows collinear antiferromagnetic order with moments of 7.1(1)mu(B) aligned in the [110] direction. Its magnetic unit cell is a new hexagonal cell with dimensions A = B = a root 3 and C = 2c. T he same magnetic structure is observed between 3 and 9.5 K in HoPtSn, but the moments of 8.0(1)mu(B) at 4 K are directed along the c-axis. B elow 3 K a spiral antiferromagnetic ordering described by the wave vec tor k = [0.352, 0, 0.464] was found. The magnetic moment at 1.9 K is 8 .0(1)mu(B). The onset of magnetic order below 3.5 K was observed in Er PtSn. Neutron diffractogram recorded at 1.6 K shows only diffuse peaks of magnetic origin.