Evolution of the superconducting transition temperature upon a substitution of Pd by Pt in Li₂(Pd_1-xPt_x)₃B (x=0-1)

We investigate on the evolution of the superconducting transition temperature upon a substitution of Pd by Pt in the noncentrosymmetric superconductor Li₂(Pd_1-xPt_x)₃B. The spin singlet and spin triplet superconducting states can coexist in noncentrosymmetric crystal structures like Li₂T₃B (T=Pt, Pd), while it is prohibited in ordinary crystal structures. This study is conducted to investigate the crossover nature in Li₂ (Pd _1-xPt_x) ₃B (x=0-1) for obtaining information on the parity mixing. We have succeeded in synthesizing samples which have higher T_c than previous results around x=1. A lot of samples have been synthesized with different ratios of x, and we found that the value of T _c changed continuously and there was no clear discontinuity between spin singlet dominant (x∼0) and spin triplet dominant (x∼1) state in T_c value, although the x dependence of T_c is decreasing nonlinearly with the increase of x. The higher x region around x∼0.8 seems to be suppressed from linear behaviour.