Magnetization of hysteretic superconductors for complete field penetration and a critical-state model with <i>Jc(H)=α/H</i>

Ohmer, M. C.; Heinrich, John P.

doi:10.1063/1.1662453

Cited by 18 publications

(5 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For simplicity we take these superconducting droplets as cylinders of radius R, which is sufficient small in order to have a constant charge density n and consequently the critical temperature T c (n) is the same within such cylinder region (As the temperature decreases, more droplets appear and the superconducting regions increases by aggregation of droplets of different n). The CSM approach leads to the magnetic field dependence of the magnetization in each small cylinder as 26 :…”

Section: The Modelmentioning

confidence: 99%

“…In order to estimate the M (B) we follow the ideas and the procedures of the CSM to each superconducting droplet. Upon applying an external magnetic field, a critical current (J c ) is established which opposes the field as J c (B) = α(T )/B according to Ohmer et al 26 . α(T ) is a temperature-dependent local constant which we have taken to be proportional to (T c (n(r)) − T ).…”

Section: The Modelmentioning

confidence: 99%

See 1 more Smart Citation

Theory of the diamagnetism above the critical temperature for cuprates

González

Mello

2004

Phys. Rev. B

View full text Add to dashboard Cite

Recently experiments on high critical temperature superconductors have shown that the doping levels and the superconducting gap are usually not uniform properties but strongly dependent on their positions inside a given sample. Local superconducting regions may develop at the pseudogap temperature (T * ) and upon cooling, grow continuously. As one of the consequences a large diamagnetic signal above the superconducting critical temperature (Tc) has been measured by different groups. Here we construct a general theory to a disordered superconductor using a critical-state model for the magnetic response to the local superconducting domains between T * and Tc and show that the resulting diamagnetic signal is in agreement with the experimental results.pacs74. 74.25.Ha,

show abstract

Section: The Modelmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Theory of the diamagnetism above the critical temperature for cuprates

González

Mello

2004

Phys. Rev. B

View full text Add to dashboard Cite

Recently experiments on high critical temperature superconductors have shown that the doping levels and the superconducting gap are usually not uniform properties but strongly dependent on their positions inside a given sample. Local superconducting regions may develop at the pseudogap temperature (T * ) and upon cooling, grow continuously. As one of the consequences a large diamagnetic signal above the superconducting critical temperature (Tc) has been measured by different groups. Here we construct a general theory to a disordered superconductor using a critical-state model for the magnetic response to the local superconducting domains between T * and Tc and show that the resulting diamagnetic signal is in agreement with the experimental results.pacs74. 74.25.Ha,

show abstract

“…Upon applying an external magnetic field, a critical current (J c ) is established which opposes the field as J c (B) = α(T )/B according to Ohmer et al [6].…”

Section: The Model For the Magnetizationmentioning

confidence: 99%

Unconventional magnetic properties of cuprates

González¹,

Caixeiro²,

Mello³

2003

Braz. J. Phys.

View full text Add to dashboard Cite

Recently experiments on high critical temperature superconductors have shown that the doping levels and the superconducting gap are usually not uniform properties but strongly dependent on their positions inside a given sample. We show here that the large diamagnetic signal above the critical temperature T c and the unusual temperature dependence of the upper critical field H c2 with the temperature can be explained taking the inomogeneities and a distribution of different local critical temperatures into account.There are increasing evidences that high critical temperature superconductors (HTSC) are intrinsic inhomogeneous materials. This is probably the cause of several unconventional behavior. In particular, recent magnetic imaging through a scanning superconducting quantum device (SQUID) microscopy has displayed a static Meissner effect at temperatures as large as three times the T c of an underdoped LSCO film [1]. Following up SQUID magnetization measurements on powder oriented YBCO and LSCO single crystals [2,3] have shown a rather high magnetic response which, due to its large signal and structure, cannot be attributed solely to the Ginzburg-Landau (GL) theory of fluctuating superconducting magnetization [4,8]. On the other hand the H-T phase diagram of the HTSC possess, in certain cases, positive curvature for H c2 (T ), with no evidence of saturation at low temperatures [5]. These lack of saturation at low temperatures may minimize the importance of strong fluctuations of the order parameter.In this paper we develop a unified view for all these anomalous properties. The basic ideas are [9,10]: the charge distribution inside a HSCT is highly inhomogeneous and may be divided in two types. A hole-poor branch which represents the AF domains and a hole-rich which characterizes the metallic regions. The width of the metallic distribution decreases with the average doping since usually, the samples becomes more homogeneous as the average doping level or average charge density increases. Due to the spatially varying local charge density, it is also expected that the T c , instead of being a single value as in usual metallic superconductors, becomes locally dependent. Therefore a given HTSC compound with an average charge density n m possess a distribution of charge density n(r), zero temperature superconducting gap ∆ 0 (r) and superconducting critical temperature T c (r) where the symbol (r) means a point inside the sample. In this scenario we identify the largest T c (r) with the the pseudogap temperature T * of the compound [11]. Metallic domains with low (high) doping level have high (low) T c (r). Upon cooling below T * the superconducting regions develop at isolated regions as droplets of rain in the air and, eventually they percolates at the superconducting critical temperature T c of the compound at which superconducting long range order is established. The Model for the MagnetizationIn order to estimate the M (B) we follow the ideas and the procedures of the Critical State Model (CSM) to each supercondu...

show abstract

“…According to the Lorentz-forcedependent critical state model, 17,18 the critical current density is given by…”

Section: B Critical State Modelmentioning

confidence: 99%

Anisotropy and field dependence of critical current density in YBa2Cu3O7−δ epitaxial thin film

Cao

Wang

Fang

et al. 1997

Journal of Applied Physics

View full text Add to dashboard Cite

The critical current density Jc of the epitaxial YBa2Cu3O7−δ thin film was measured as a function of applied magnetic field H up to 6 T for three special configurations: (1) H∥c axis and H⊥J; (2) H⊥c axis and H⊥J; (3) H⊥c axis and H∥J. We observed a large anisotropy of Jc(H) between H∥c axis and H⊥c axis with H⊥J, and a very small anisotropy of Jc(H) between H∥J and H⊥J with H⊥c axis. The field dependence of the critical current density can be well described by the modified Kim–Anderson model taking into account the Kramer scaling law. The weak dependence of the transport critical current density on its orientation relative to the applied magnetic field is discussed.

show abstract

Magnetization of hysteretic superconductors for complete field penetration and a critical-state model with Jc(H)=α/H

Cited by 18 publications

References 9 publications

Theory of the diamagnetism above the critical temperature for cuprates

Theory of the diamagnetism above the critical temperature for cuprates

Unconventional magnetic properties of cuprates

Anisotropy and field dependence of critical current density in YBa2Cu3O7−δ epitaxial thin film

Contact Info

Product

Resources

About