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 compo unds R2PtSi3, where R = La, Ce, Pr, Nd, Gd and Y, crystallize in an AlB2 he xagonal structure. The results of electrical resistivity, heat capacity, ma gnetic susceptibility and isothermal magnetization (M) measurements are als o reported. The results reveal that the Cc, Nd and Gd compounds order magne tically 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 lo ops, isothermal M behavior and positive paramagnetic Curie temperature (the ta (p)), and Pr exhibits a complex type of magnetic behavior. La and Y comp ounds remain nonmagnetic as expected down to 2 K. There is a breakdown of d e 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 tempera ture theta (p) is positive. It is stressed that there is a prominent minimu m in the temperature dependence of rho around 40K (well above T-C) in Gd2Pt Si3, 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 precurs or effects mimicking the Kondo effect, known till date. (C) 2001 Elsevier S cience B.V. All rights reserved.