非中心对称超导体Mg_(10±δ)Ir_(19)B_(16■δ)的超导电性研究

Superconducting proprties of noncentrosymmetric Mg_(10±δ)Ir_(19)B_(16■δ)

Mg10±δIr19B16■δ是具有非中心对称性的超导材料.通过对两种组分的样品Mg9.3Ir19B16.7和Mg11Ir19B15的比热测量,得到了这类超导体的超导态和正常态的特征参数:包括转变温度TC,正常态态密度N(EF),德拜温度ΘD,上临界场HC2等.并由此求出Ginzburg-London相干长度ξGL,穿透深度λGL,下临界场HC1和热力学临界场HC.这些参数因化学组分不同而变化.高的N(EF)和ΘD对应高的TC,因此也具有较高的HC2.另外比热跃变ΔC/γnTC=1.66和电声子耦合常数λ=0.58不随化学组分变化,表明此超导体是中等强度耦合的第二类超导体.

Two non-centrosymmetric superconductors Mg0.3 Ir19 B16.7 and Mg11 Ir19 Bl5 are synthesized. The normal state electronic coefficient of specific heat γn, the Debye temperature （Θt） and the superconducting upper critical field He2 are found to be sample-dependent, while the electron-phonon interaction constant A = 0.58 and the normalized specific heat jump ΔC/γn Tc = 1.66 are sample - independent. The higher superconducting transition temperature （ Tc = 5.7K） in Mg0.3Ir19Bi6.7 is found to be due to the higher density of states and higher Debye temperature ΘD compared with that of Mg44 Irl9 B15 . We also obtained other characteristic parameters of both superconductors, including the Ginzburg-London coherence ξGL, penetration λCL, lower critical field HCl and thermodynamic critical field Hc.