Antiferromagnetic properties of ternary silicides RNiSi (R = Tb-Er)

Neutron diffraction and magnetometric measurements show that RNiSi (R = Tb- Er) compounds are antiferromagnetic at low temperatures. At 1.5 K, TbNiSi e xhibits a square-modulated order of magnetic moments which transforms at 9 K into a sine-modulated magnetic structure stable up to the Neel point at 1 6 K. The same magnetic behavior was found in DyNiSi with the magnetic phase transition at 3 K and the Neel point at 8.8 K. At 1.5 K, the antiferromagn etic order in HoNiSi is collinear described by the wave vector \1/2, 0, 1/2 \. The ordering changes to a sine-modulated structure with the wave vector \0.53, 0.18, 0.336\ at 3.2 K and vanishes at the Neel point at 4.1 K. A col linear antiferromagnetic structure with the wave vector \0, 1/2, 1/4\ was f ound at 1.5 K in ErNiSi. It transforms at 2.2 IC. into a sine-modulated ord er described by the wave vector \0.197, 0.515, 0.154\. The Neel point is at 3.3 K. In RNiSi (R = Tb, Dy, Ho) the magnetic moment was found to be align ed along the b-axis, while in ErNiSi it is localized in the (a-c) plane. In all compounds the magnitude of the ordered magnetic moment at 1.5 K amount s nearly to the free ion values for the respective R3+ ions. (C) 1999 Elsev ier Science B.V. All rights reserved.