Electromagnetic Absorption in the Copper Oxide Superconductors
Electromagnetic Absorption in the Copper Oxide Superconductors

Author: Frank J. Owens

Publisher: Springer Science & Business Media

Published: 1999-01-31

Total Pages: 208

ISBN-13: 0306459485

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In 1987 a major breakthrough occurred in materials science. A new family of materials was discovered that became superconducting above the temperature at which nitrogen gas liquifies, namely, 77 K or –196°C. Within months of the discovery, a wide variety of experimental techniques were brought to bear in order to measure the properties of these materials and to gain an understanding of why they superconduct at such high temperatures. Among the techniques used were electromagnetic absorption in both the normal and the superconducting states. The measurements enabled the determination of a wide variety of properties, and in some instances led to the observation of new effects not seen by other measu- ments, such as the existence of weak-link microwave absorption at low dc magnetic fields. The number of different properties and the degree of detail that can be obtained from magnetic field- and temperature-dependent studies of electromagnetic abso- tion are not widely appreciated. For example, these measurements can provide information on the band gap, critical fields, the H–T irreversibility line, the amount of trapped flux, and even information about the symmetry of the wave function of the Cooper pairs. It is possible to use low dc magnetic field-induced absorption of microwaves with derivative detection to verify the presence of superconductivity in a matter of minutes, and the measurements are often more straightforward than others. For example, they do not require the physical contact with the sample that is necessary when using four-probe resistivity to detect superconductivity.

Electromagnetic Absorption in the Copper Oxide Superconductors
Electromagnetic Absorption in the Copper Oxide Superconductors

Author: Frank J. Owens

Publisher: Springer

Published: 2013-03-22

Total Pages: 199

ISBN-13: 9781475787603

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In 1987 a major breakthrough occurred in materials science. A new family of materials was discovered that became superconducting above the temperature at which nitrogen gas liquifies, namely, 77 K or –196°C. Within months of the discovery, a wide variety of experimental techniques were brought to bear in order to measure the properties of these materials and to gain an understanding of why they superconduct at such high temperatures. Among the techniques used were electromagnetic absorption in both the normal and the superconducting states. The measurements enabled the determination of a wide variety of properties, and in some instances led to the observation of new effects not seen by other measu- ments, such as the existence of weak-link microwave absorption at low dc magnetic fields. The number of different properties and the degree of detail that can be obtained from magnetic field- and temperature-dependent studies of electromagnetic abso- tion are not widely appreciated. For example, these measurements can provide information on the band gap, critical fields, the H–T irreversibility line, the amount of trapped flux, and even information about the symmetry of the wave function of the Cooper pairs. It is possible to use low dc magnetic field-induced absorption of microwaves with derivative detection to verify the presence of superconductivity in a matter of minutes, and the measurements are often more straightforward than others. For example, they do not require the physical contact with the sample that is necessary when using four-probe resistivity to detect superconductivity.

Microwave Studies of High Tc Copper Oxide Superconductors and NbN
Microwave Studies of High Tc Copper Oxide Superconductors and NbN

Author: Chi-Chung Chin

Publisher:

Published: 1991

Total Pages: 96

ISBN-13:

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This report covers several projects, namely: surface impedance measurements using both stripline and cavity resonators; microwave magnetic field dependence measurements of the surface impedance of NbN; determination of the upper critical field of YBa2Cu3O7 by microwave measurements; and the calculation of the angular dependence of an anisotropic superconductor. The temperature and frequency dependencies of the surface impedance of NbN thin films were measured using a stripline resonator from 4.2 to 13 K and from 0.5 to 10 GHz. At 4.2 K resonant cavity measurements of the surface resistance were made at 35 and 56 GHz. From the surface reactance measurements using both cavity and stripline techniques, we obtain the penetration depth extrapolated to T=0 K. Lamba(0)=3700A. For the stripline, the film thickness was approximately 8000 angstrom, which is about twice the measured penetration depth. The weak-coupling (full) Mattis-Bardeen theory appropriate for NbN was used to fit the temperature dependence on the surface resistance. Based on the quality of the weak-coupling fit to the data, we conclude that the strong-coupling effect is not important in the local and dirty limits. The correction of the stripline measurements of the surface resistance due to the finite film thickness is discussed.

Electromagnetic Absorption in the Copper Oxide Superconductors
Electromagnetic Absorption in the Copper Oxide Superconductors

Author: Frank J. Owens

Publisher: Springer Science & Business Media

Published: 2006-04-11

Total Pages: 208

ISBN-13: 0306470829

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In 1987 a major breakthrough occurred in materials science. A new family of materials was discovered that became superconducting above the temperature at which nitrogen gas liquifies, namely, 77 K or –196°C. Within months of the discovery, a wide variety of experimental techniques were brought to bear in order to measure the properties of these materials and to gain an understanding of why they superconduct at such high temperatures. Among the techniques used were electromagnetic absorption in both the normal and the superconducting states. The measurements enabled the determination of a wide variety of properties, and in some instances led to the observation of new effects not seen by other measu- ments, such as the existence of weak-link microwave absorption at low dc magnetic fields. The number of different properties and the degree of detail that can be obtained from magnetic field- and temperature-dependent studies of electromagnetic abso- tion are not widely appreciated. For example, these measurements can provide information on the band gap, critical fields, the H–T irreversibility line, the amount of trapped flux, and even information about the symmetry of the wave function of the Cooper pairs. It is possible to use low dc magnetic field-induced absorption of microwaves with derivative detection to verify the presence of superconductivity in a matter of minutes, and the measurements are often more straightforward than others. For example, they do not require the physical contact with the sample that is necessary when using four-probe resistivity to detect superconductivity.