文档介绍：
超薄 MgB2 薄膜的临界电流密度随温度和磁
场的变化#
张辰,王达,张焱,王越**
5
10
(北京大学物理学院,北京 100871)
摘要:利用紫外曝光配合 Ar 离子刻蚀、FIB 后续加工的方法,在 10 nm 厚的 MgB2 薄膜上
制备了宽度在微米到亚微米不等的超导微桥。通过对这些微桥的电学输运性质的测量,研究
了超薄 MgB2 薄膜的临界电流密度 Jc 随温度和磁场的变化。结果发现 Jc 随温度的变化符合
传统的 G-L 理论预言。当施加有垂直于膜面的磁场时,Jc 随磁场的升高而下降,而且随着
温度的升高 Jc 的下降更明显,表明磁通线进入超导体的边界势垒随着温度的升高而逐渐变
弱。实验中还观察到 FIB 加工对临界电流密度有一定的增强效应。
关键词:凝聚态物理;MgB2;超薄薄膜;临界电流密度
中图分类号:O469
15
Temperature and ic field dependence of critical
current densities in MgB2 ultrathin films
ZHANG Chen, WANG Da, ZHANG Yan, WANG Yue
(School of Physics, Peking University, Beijing 100871)
20
25
30
35
Abstract: In this paper, microbridges with widths ranging from microns to submicrons were
fabricated in 10 nm thick MgB2 ultrathin films using ultra-violet lithography, Ar ion etching and
FIB methods. Electrical transport properties of these microbridges were measured and the
dependencies of the critical current density Jc on the temperature and ic field were
investigated. It was found that the temperature dependence of the Jc could be well described by
the traditional G-L theory. When applying a ic field perpendicular to the film surface, the
Jc decreased with increasing field and this trend was more evident when raising the temperature,
implying that the edge barrier for flux line to enter MgB2 microbridges e lower as the
temeprature rises. It was also osbserved that the process o