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

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 Cc, 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 (theta (p)), and Pr exhibits a complex type of magnetic behavior. La and Y compounds remain nonmagnetic 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 theta (p) is positive. It is stressed that there is a prominent minimum in the temperature dependence of rho around 40K (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. (C) 2001 Elsevier Science B.V. All rights reserved.