Magnetic properties and structural data of ternary silicides: (RE,Th,U) Os2Si2 (RE= rare earth)

New ternary silicides (RE,Th,U) Os₂Si₂ have been synthesized from the elements. All the compounds (RE= Y,La,Ce,Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb, Lu) were found to be isotypic and to crystallize with the ordered BaAl₄-type of structure (ThCr₂Si₂-type). Magnetic properties of these alloys — studied in the temperature range 1.5<T<1100 K — reveal a typical Van Vleck paramagnetism of free RE³⁺ ions at temperatures higher than 300 K. The observed effective paramagnetic moment of CeOs₂Si₂, μ(eff)=0.98 BM, is compatible with a rather low concentration (15%) of Ce³⁺. The effective moment of SmOs₂Si₂, μ(eff)=0.47 BM, is in reasonable agreement with a Hund's rule $\text{J=}\text{5}\text{2}$ ground level for free Sm³⁺. For temperatures above 25 K, the magnetic susceptibility as a function of temperature corresponds to the Van Vleck behavior for free Sm³⁺ (closely spaced multiplet, $\text{J=}\text{5}\text{2}$,$\text{J=}\text{7}\text{2}$. Magnetic ordering temperatures of REOs₂Si₂ silicides are generally below 42 K. (Pr,Nd,Ho,Er,Tm) Os₂Si₂ exhibit ferromagnetic ordering whereas (Sm,Gd, Tb,Dy) Os₂Si₂ show antiferromagnetic behavior. Above 1.8 K none of the samples was found to be superconducting.