On the determination of vortex creep parameters in superconductors using standard magnetization relaxation data
On the determination of vortex creep parameters in superconductors using standard magnetization relaxation data
复制标题
利用标准磁化弛豫数据确定超导体涡旋蠕变参数
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
L. Miu
中科院分区：
文献类型：
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作者：
I. Ivan;D. Miu;S. Popa;G. Jakob;L. Miu
在零场冷却条件下，研究了YBa_2Cu_3O_7（YBCO）薄膜的不可逆磁矩m（t）随温度T和外加磁场H（沿c轴沿着）的变化规律，用于确定涡旋蠕变参数.数据分析使用归一化涡旋蠕变激活能的T和电流密度依赖性进行，或者通过在一般涡旋蠕变方程的框架中用众所周知的插值公式拟合m（t）数据进行。结果表明：（1）即使在静态钉扎强度很强的情况下，在低T范围内，特征钉扎能仍然很小，在低T范围内，标准磁化强度测量中出现的涡旋蠕变是弹性的，（ii）随着H的增加，蠕变时间尺度的显著增加和蠕变指数的降低超出了理论预测，这可以归因于弹性-蠕变-塑性的交叉。蠕变产生的宏观电流在磁化测量过程中在试样中感应，和（iii）蠕变参数提取的插值公式是高度受短t记录的m（t）数据，这可能会导致非物理蠕变参数值。
The relaxation of the irreversible magnetic moment m(t) in YBa2Cu3O7 (YBCO) films was investigated as a function of temperature T and the external magnetic field H along the c axis applied in zero-field cooling conditions, for the determination of vortex creep parameters. The data analysis was performed using the T and current density dependence of the normalized vortex creep activation energy, or by the fit of the m(t) data with the well known interpolation formula in the framework of the general vortex creep equation. It was found that (i) even for specimens with strong static pinning the characteristic pinning energy remains small in the low-T range, where the vortex creep appearing in standard magnetization measurements is elastic, (ii) the observed strong increase of the time scale for creep and the decrease of the creep exponent with increasing H beyond the theoretical predictions can be attributed to the crossover elastic-creep–plastic-creep generated by the macroscopic currents induced in the specimen during magnetization measurements, and (iii) the creep parameters extracted with the interpolation formula are highly affected by the m(t) data registered at short t, which may lead to unphysical creep parameter values.