Low temperature dependence of the penetration depth in YBCO thin films revisited by mm wave transmission and surface impedance measurements

We present a number of experimental results on the temperature dependence of the magnetic penetration depth λ and on the temperature and field dependence of the microwave surface impedance Z s =R s +iX s in both pellets and thin films of MgB2 , exhibiting critical temperatures ranging between 26 and 38 K. Accurate measurements of Z s (H,T) were performed by means of a sapphire dielectrically loaded cavity operating in the microwave region (20 GHz). The study of λ(T) was carried out employing a single coil mutual inductance technique in the MHz region. An anisotropic s-wave BCS model can account for the temperature dependence experimentally observed in the penetration depth data of the best films, confirming previous reports on the conventional nature of superconductivity in diborides. On the contrary, films having a reduced value of the critical temperature and pellets show no evidence of saturation, and the experimental results strictly follow a quadratic dependence down to the lowest temperatures. We explain this behavior with the presence of metallic Mg inclusions that may locally depress the gap. The study of the surface impedance versus temperature and field shows also that the source of microwave loss can be markedly different, depending on the structural and transport properties of the samples.

Download Full-text

The low temperature dependence of magnetization of as-deposited Fe-Hf-C-N nanocrystalline thin films

Nanostructured Materials ◽

10.1016/s0965-9773(99)00306-2 ◽

1999 ◽

Vol 12 (5-8) ◽

pp. 1097-1102 ◽

Cited By ~ 1

Author(s):

K.S. Kirn ◽

Y.H. Seong ◽

S.C. Yu ◽

S.H. Han ◽

H.J. Kim

Keyword(s):

Thin Films ◽

Low Temperature ◽

Temperature Dependence ◽

Nanocrystalline Thin Films

Download Full-text

Substrate temperature dependence of the texture quality in YBCO thin films fabricated by on-axis pulsed-laser ablation

Superconductor Science and Technology ◽

10.1088/0953-2048/10/1/006 ◽

1997 ◽

Vol 10 (1) ◽

pp. 41-46 ◽

Cited By ~ 40

Author(s):

B L Low ◽

S Y Xu ◽

C K Ong ◽

X B Wang ◽

Z X Shen

Keyword(s):

Thin Films ◽

Laser Ablation ◽

Substrate Temperature ◽

Temperature Dependence ◽

Pulsed Laser ◽

Pulsed Laser Ablation ◽

Ybco Thin Films

Download Full-text

Temperature dependence of the magnetic penetration depth in Nb, NbCN and YBa2Cu3O7-δ thin films

Physica B Condensed Matter ◽

10.1016/0921-4526(91)90381-n ◽

1991 ◽

Vol 169 (1-4) ◽

pp. 671-672 ◽

Cited By ~ 2

Author(s):

S.M. Anlage ◽

B.W. Langley ◽

G. Deutscher ◽

R.W. Simon ◽

J.M. Murduck ◽

...

Keyword(s):

Thin Films ◽

Temperature Dependence ◽

Penetration Depth ◽

Magnetic Penetration Depth ◽

Magnetic Penetration

Download Full-text

Magnetic Penetration Depth Measurements and Inhomogeneity in YBa2Cu3O7−δ Superconducting Thin Films

MRS Proceedings ◽

10.1557/proc-195-333 ◽

1990 ◽

Vol 195 ◽

Cited By ~ 2

Author(s):

Steven M. Anlage ◽

Brian W. Langley ◽

Jurgen Halbritter ◽

Chang-Beom Eom ◽

Neil Switz ◽

...

Keyword(s):

Thin Films ◽

Temperature Dependence ◽

Penetration Depth ◽

Exponential Decay ◽

Power Law ◽

Low Temperatures ◽

Bcs Theory ◽

Magnetic Penetration Depth ◽

Microstrip Resonator ◽

Magnetic Penetration

ABSTRACTThe microstrip resonator technique has been applied to study the temperature dependence of the magnetic penetration depth in high quality YBa2Cu3O7−δ thin films. The temperature dependence at low temperatures comes out directly from measured data, with no assumptions about transmission line geometry, dielectric properties, or a model for the temperature dependence of the penetration depth. One can interpret the data in terms of either an exponential decay of λ(T) at low temperatures or as a power law decay. The energy gaps obtained from the exponential decay at low temperature are found to be significantly smaller than weak coupled BCS theory and power-law exponents are in the range of 1.3 to 3.2. These results will be discussed in terms of microscopic theories and the possibility that materials properties dominate the measurement.

Download Full-text