Magnetic structure of the ferromagnetic new ternary silicide Nd5CoSi2
Résumé
Nd5CoSi2 was obtained from the elements by arc-melting followed by annealing at 883 K. Its investigation by single-crystal x-ray and neutron powder diffraction shows that this ternary silicide crystallizes as Nd5Si3 in a tetragonal structure deriving from the Cr5B3-type (I4/mcm space group; a = 7.7472(2) and c = 13.5981(5) Å as unit cell parameters). The structural refinements confirm the mixed occupancy on the 8h site between Si and Co atoms, as already observed for Gd5CoSi2. Magnetization and specific heat measurements reveal a ferromagnetic behavior below TC = 55 K for Nd5CoSi2. This magnetic ordering is further evidenced by neutron powder diffraction investigation revealing between 1.8 K and TC a canted ferromagnetic structure in the direction of the c-axis described by a propagation vector k = (0 0 0). At 1.8 K, the two Nd3+ ions carry ordered magnetic moments equal respectively to 1.67(7) and 2.37(7) μB for Nd1 and Nd2; these two moments exhibit a canting angle of θ = 4.3(6)°. This magnetic structure presents some similarities with that reported for Nd5Si3.