Magnetic transitions of superconducting thin films and foils. II. Tin
Magnetic transitions of superconducting thin films and foils. II. Tin
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超导薄膜和箔的磁转变。
DOI：
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发表时间：
1968
期刊：
影响因子：
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通讯作者：
G. Cody
中科院分区：
文献类型：
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作者：
R. Miller;G. Cody
通过横向磁化和交流磁化率测量，确定了纯Pb薄膜和箔的垂直和平行磁跃迁作为厚度（400 AA{}至35 ensuremath{mu}）和温度（1.4至4.2ifmmode^ cirelexdegreefi {}K）的函数。对于厚度小于临界厚度${d}_{c}ensuremath{约}15$ kAA{}的垂直临界场（${H}_{ensuremath{perp}}$），如果假设穿透深度与厚度相关，则与Tinkham理论非常吻合。${d}_{c}$以上的厚度数据遵循由正表面能对中间态自由能的影响所预测的厚度依赖关系。${d}_{c}$在${H}_{ensuremath{perp}}$中有一个最小值。到${d}_{c}$的平行临界场（${H}_{ensuremath{parallel}}$）与圣·詹姆斯和德·热纳的二阶跃迁理论符合得很好。在${d}_{c}$上面，${H}_{ensuremath{parallel}}$与用于lead的${H}_{c3}$的批量值一致。在${d}_{c}$附近，磁化曲线开始呈现一条可逆的尾巴，这条尾巴持续到更大的厚度，其斜率与理论基本一致。从数据中，计算了$ensuremath{kappa}(T)$、$ensuremath{lambda}(T)$、${ensuremath{lambda}}_{L}(0)$和${ensuremath{xi}}_{0}$的体积值，以及这些量与厚度的依赖关系。
The perpendicular and parallel magnetic transitions for pure Pb films and foils have been determined from transverse magnetization and ac susceptibility measurements as a function of thickness (400 AA{} to 35 ensuremath{mu}) and temperature (1.4 to 4.2ifmmode^circelse extdegreefi{}K). The perpendicular critical field (${H}_{ensuremath{perp}}$) for thicknesses less than a critical thickness, ${d}_{c}ensuremath{approx}15$ kAA{}, is in good agreement with the theory of Tinkham if it is assumed that the penetration depth is thickness-dependent. The data for thicknesses above ${d}_{c}$ follow a thickness dependence predicted from the effect of a positive surface energy on the free energy of the intermediate state. At ${d}_{c}$ there is a minimum in ${H}_{ensuremath{perp}}$. The parallel critical field (${H}_{ensuremath{parallel}}$) up to ${d}_{c}$ is in good agreement with the theory of Saint James and de Gennes for a second-order transition. Above ${d}_{c}$, ${H}_{ensuremath{parallel}}$ agrees with the bulk value of ${H}_{c3}$ for lead. In the vicinity of ${d}_{c}$ the magnetization curve starts to exhibit a reversible tail which persists to larger thicknesses and whose slope is in reasonable agreement with theory. From the data, the bulk values of $ensuremath{kappa}(T)$, $ensuremath{lambda}(T)$, ${ensuremath{lambda}}_{L}(0)$, and ${ensuremath{xi}}_{0}$, as well as the thickness dependence of these quantities, have been computed.