采用两步固相反应法，在母相FeAs=1111结构的NdFeAsO中掺入BaF2，实现电子与空穴的双掺杂．该体系超导转变温度（Tc）在33-50K范围，取决于名义BaF2掺杂量x．在实验范围内，掺杂量越大，转变温度越高，当x=0．2时，Tc达到50K．磁电阻测量表明：高掺杂量样品（例如x=0．2）具有较高的上临界场（Hc2）和不可逆场（Hirr），其剩余电阻率（RRR）也较大．交流磁化率和磁化临界电流密度研究表明，低磁场下磁通耗散在10^-2～10^-4秒时间窗口变化并不明显，而高应用磁场下其磁通钉扎力密度（Fp）对温度依赖性强，中高温区下降到小于10MN／m^3．表明：高磁热状态下，当前多晶体样品的磁通钉扎性能有待提高．
Binary doping effect is studied for the Fe-based superconductors of Nd1-xBaxFeAsO1-2xF2x（x= 0. 05, 0. 1, 0. 15, 0. 2） synthesized by two step solid state reaction. Temperature dependences of electric resistivity reveal that the superconductivity for the studied system emerges at x = 0. 1, and enhances together with irreversibility fields （Hirr） and upper critical fields （He2） as the doping content x increases further. In case of x= 0. 2, the superconducting critical temperature （To） reaches as high as 50K, the ac susceptibility and critical current density indicate the similar flux dissipation behavior within the time windows of 10 ^-2 -10^-4, while the strong temperature dependence of flux pinning but low pinning force density （Fp）, decreasing to several MN/ma at middle to high temperature region. This suggests the current polycrystalline samples should be improved in high magneto-thermal state.
参考文献
| [1] | REN Zhi-An,LU Wei,YANG Jie,YI Wei,SHEN Xiao-Li,LI Zheng-Cai,CHE Guang-Can,DONG Xiao-Li,SUN Li-Ling,ZHOU Fang,ZHAO Zhong-Xian.Superconductivity at 55 K in Iron-Based F-Doped Layered Quaternary Compound Sm[O1-xFx]FeAs[J].中国物理快报（英文版）,2008(06):2215-2216. |
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