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

Abstract

Neutron diffraction and magnetometric measurements show that RNiSi (R=Tb–Er) compounds are antiferromagnetic at low temperatures. At 1.5 K, TbNiSi exhibits a square-modulated order of magnetic moments which transforms at 9 K into a sine-modulated magnetic structure stable up to the Néel point at 16 K. The same magnetic behavior was found in DyNiSi with the magnetic phase transition at 3 K and the Néel point at 8.8 K. At 1.5 K, the antiferromagnetic 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 Néel point at 4.1 K. A collinear antiferromagnetic structure with the wave vector |0, 1 2 , 1 4 | was found at 1.5 K in ErNiSi. It transforms at 2.2 K into a sine-modulated order described by the wave vector |0.197, 0.515, 0.154|. The Néel point is at 3.3 K. In RNiSi (R=Tb, Dy, Ho) the magnetic moment was found to be aligned 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 amounts nearly to the free ion values for the respective R 3+ ions.