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

  1. Nov 18, 2013 #1
    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.
     
  2. jcsd
  3. Nov 18, 2013 #2

    ZapperZ

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    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.
     
  4. Nov 18, 2013 #3
    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).
     
  5. Nov 18, 2013 #4

    ZapperZ

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    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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