Magnetic behavior of a new series of ternary compounds of the type, R₂PtSi₃ (R=La, Ce, Pr, Nd, Gd and Y)

Abstract

We report here the formation of a new series of ternary intermetallic compounds R₂PtSi₃, where R=La, Ce, Pr, Nd, Gd and Y, crystallize in an AlB₂ hexagonal structure. The results of electrical resistivity, heat capacity, magnetic susceptibility and isothermal magnetization (M) measurements are also reported. The results reveal that the Ce, Nd and Gd compounds order magnetically around (T_C=) 5, 18 and 24 K respectively. While most of them are classified as ferromagnets on the basis of the observation of hysteresis loops, isothermal M behavior and positive paramagnetic Curie temperature (θ_p), and Pr exhibits a complex type of magnetic behavior. La and Y compounds remain non-magnetic as expected down to 2 K. There is a breakdown of de Gennes scaling of magnetic ordering temperature for Ce and Nd compounds. For the Ce compound, the Kondo effect at low temperatures is negligible, as the characteristic resistivity minimum is not observed and the low temperature θ_p is positive. It is stressed that there is a prominent minimum in the temperature dependence of ρ around 40 K (well above T_C) in Gd₂PtSi₃, and this observation is particularly notable considering that no such minimum even for the Ce compound is observed, and this is the third of this interesting class of Gd compounds, viz., those exhibiting magnetic precursor effects mimicking the Kondo effect, known till date.