How can type-I superconductors have a critical field value?

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Discussion Overview

The discussion centers around the properties of type-I superconductors, specifically addressing the concept of critical magnetic field strength and how it relates to the behavior of these materials in the presence of magnetic fields. Participants explore the implications of flux pinning and the differences between type-I and type-II superconductors.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that type-I superconductors cannot be penetrated by magnetic fields, leading to confusion about the existence of a critical magnetic field strength.
  • Others argue that type-I superconductors do have a critical magnetic field value, suggesting that the same physics that applies to type-II superconductors should also apply to type-I superconductors.
  • A participant questions the logic of discussing critical field values for type-I superconductors if they cannot have magnetic fields inside them, citing Wikipedia as a reference.
  • Another participant clarifies that type-I superconductors do not allow magnetic fields inside them in the superconducting state, but will allow penetration when the magnetic field exceeds the critical value, similar to the behavior of type-II superconductors above their upper critical field.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of type-I superconductors regarding magnetic field penetration and the significance of critical field values. The discussion remains unresolved, with no consensus reached on the interpretations of these properties.

Contextual Notes

Participants reference definitions and behaviors of superconductors that may depend on specific conditions or assumptions, such as the state of the material and the strength of the magnetic field. There is an ongoing debate about the phases of superconductivity and the implications of critical fields.

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Hello. I am reading about Flux pinning and I have read that only type-II superconductors can be used for that because there is no magnetic field in type-I superconductors (or rather they cannot be penetrated).
If so, how can type-I superconducotrs still have a critical magnetic field strength value in teslas? It seems to me they should be able to withstand any kind of a field due to their property.
 
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Gytax said:
Hello. I am reading about Flux pinning and I have read that only type-II superconductors can be used for that because there is no magnetic field in type-I superconductors (or rather they cannot be penetrated).
If so, how can type-I superconducotrs still have a critical magnetic field strength value in teslas? It seems to me they should be able to withstand any kind of a field due to their property.

Why?

To me, it is MORE unusual to have a Type Ii superconductor in which the two states are coexisting together.

If you can accept the upper critical field that exist for Type II, then the same physics apply to the critical field of Type I.

Zz.
 
I am sorry but I still do not understand how a type-I superconductor can at the same time both be penetrated and not by a magnetic field. Wikipedia says T-I SC cannot have magnetic field inside of them but that would mean there is no point in talking about critical field value (the value in teslas at which due to the strength of the magnetic field inside the SC the material loses some of its properties).
 
Gytax said:
I am sorry but I still do not understand how a type-I superconductor can at the same time both be penetrated and not by a magnetic field. Wikipedia says T-I SC cannot have magnetic field inside of them but that would mean there is no point in talking about critical field value (the value in teslas at which due to the strength of the magnetic field inside the SC the material loses some of its properties).

Er... when the field is above the critical field, Type I becomes normal and will have the field penetrating through the material! This is the same as Type II above the upper critical field. so I have no idea where you get the idea that it "... can at the same time both be penetrated and not by a magnetic field..."

It cannot have a magnetic field inside of it in the superconducting state and while it is belong the critical field. Same as below Hc1 for Type II. It just doesn't have that phase between Hc1 and Hc2 as in Type II. Above Hc for Type I is the same as above Hc2 for Type II!

Zz.
 

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