Y＿（0．9）Eu＿（0．1）Ba＿2Cu＿3O＿（7－δ）中的磁通蠕动研究

STUDIES OF FLUX CREEP IN Y_(0.9)Eu_(0.1)Ba_2Cu_3O_(7-δ)

在较宽的温度（４．２－８０Ｋ）和磁场（０－８Ｔ）范围内测量了ＹＢａ＿２Ｃｕ＿３Ｏ＿（７－δ）和Ｙ＿（０．９）Ｅｕ＿（０．１）Ｂａ＿２·Ｃｕ＿３Ｏ＿（７－δ）样品的磁滞回线和磁弛豫，研究了其Ｍ（ｔ），Ｊ＿ｃ（Ｔ）和Ｕ＿（ｅｆ＿ｆ）（Ｊ）关系，并与现有的一些理论模型所预言的结果进行了比较。结果表明：（１）与ＹＢａ＿２Ｃｕ＿３Ｏ＿（７－δ）相比，Ｙ＿（０．９）Ｅｕ＿（０．１）·Ｂａ＿２Ｃｕ＿３Ｏ＿（７－δ）样品的有效钉扎势和无磁通蠕动时的临界电流密度有明显提高，表明Ｅｕ的部分替代引入了新的、具有更大的钉扎势的钉扎中心；（２）与其它模型相比，集体钉扎——蠕动理论对我们的实验结果作了更好的描述，因而本文为这一理论提供了新的实验证据。

he magnetic hysteresis and relaxation behaviors in YBa_2Cu_3O_(7-δ) and Y_(0.9)Eu_(0.1)Ba_2Cu_3O_(7-δ) samples were measured in the wide ranges of temperature(4.2-80 K)andfield(0-8T).The M(t),J_c(T)and U_(eff)(J) relationships in these samples werestudied and several theoretical models were tested.The results show:(1) Both theeffective pinning energy and critical current density in the absence of flux creep areobviously higher in than in sample,which indicatesthe introductions of new pinning centers with larger pinning energy by the partialsubstitution of Eu for Y.(2) Compared with other models.the collective flux creeptheory gives the best description on our experimental results and thu‘ thi‘ workprovides a new experimental evidence for this theory.