NEUTRON POWDER DIFFRACTION STUDY OF THE ANTIFERROMAGNETIC COMPOUND TB2PD2.05SN0.95

Magnetic measurements and neutron diffraction experiments have been pe rformed on a Tb2Pd2.05Sn0.95 polycrystalline sample. Two antiferromagn etic transitions are obtained at T-N = 27.3(2) K and T-2 = 20.8(5) K, respectively. The magnetic structure between T-N and T-2 is characteri zed by an incommensurate wave vector k(1) = (k(x) k(x) 1/2) (with a co ntinuous decrease of the incommensurate component k(x) from k(x) = 0.1 15(5) at T = 26.3 K to k(x) = 0.070(5) at T = 20.8 K). Below T-2, a co mmensurate magnetic structure is observed, with k(2) = (0 0 1/2) wave vector (k(x) locked to zero). This low temperature magnetic structure is described as a non-collinear arrangement of terbium magnetic moment s along the [110] and [1(1) over bar0$] directions of the tetragonal u nit cell, according to the Gamma(10) irreducible representation of the wave vector group. The value of the ordered magnetic moment is equal to 8.70(5) mu(B)/Tb3+ at T = 1.5 K. (C) 1997 Elsevier Science S.A.