Absolute values of the London penetration depth in YBa2Cu3O6+y measured by zero field ESR spectroscopy on Gd doped single crystals

作者：Pereg Barnea T^*; Turner PJ; Harris R; Mullins GK; Bobowski JS; Raudsepp M; Liang RX; Bonn DA; Hardy WN

来源：Physical Review B, 2004, 69(18): 184513.

DOI：10.1103/PhysRevB.69.184513

Zero-field electron spin resonance (ESR) of dilute Gd ions substituted for Y in the cuprate superconductor YBa2Cu3O6+y is used as a novel technique for measuring the absolute value of the low-temperature magnetic penetration depth lambda(T-->0). The Gd ESR spectrum of samples with approximate to1% substitution was obtained with a broadband microwave technique that measures power absorption bolometrically from 0.5 to 21 GHz. This ESR spectrum is determined by the crystal field that lifts the level degeneracy of the spin 7/2 Gd3+ ion and details of this spectrum provide information concerning oxygen ordering in the samples. The magnetic penetration depth is obtained by relating the number of Gd ions exposed to the microwave magnetic field to the frequency-integrated intensity of the observed ESR transitions. This technique has allowed us to determine precise values of lambda for screening currents flowing in the three crystallographic orientations ((a) over cap, (b) over cap, and (c) over cap) in samples of GdxY1-xBa2Cu3O6+y of three different oxygen contents y=0.993 (T-c=89 K), y=0.77 (T-c=75 K), and y=0.52 (T-c=56 K).

• 出版日期2004-5