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Superconductivity perfect diamagnetism

The Meissner Effect and Levitation. Besides the absence of electrical resistance, a superconducting material is characterized by perfect diamagnetism. The exclusion of magnetic field lines from a material when it passes from a normal state to a superconducting state is shown schematically in Figure 3. [Pg.500]

As discussed earlier, the original BCS theory predicted that superconductors were perfect diamagnets. It was therefore with surprise that solids were recently discovered that are both ferromagnetic and superconducting. [Pg.408]

In addition to the zero resistivity, superconducting materials are perfectly diamagnetic in other words, magnetic fields (up to a limiting strength that decreases as the temperature rises toward Tc) cannot penetrate them (the Meissner effect). This is a consequence of the mobile, paired state of the electrons. Indeed, it is the demonstration of the Meissner effect, rather than lack of electrical resistivity, that is usually demanded as evidence of superconductive behavior. One entertaining consequence of the Meissner effect is that small but powerful magnets will float (levitate) above the surface of a flat, level superconductor.30... [Pg.424]

Superconductivity Simultaneous disappearance of electrical resistivity and the appearance of perfect diamagnetism in a material. [Pg.170]

Research activity in the field of superconductivity has been extensive and continues to be of interest globally. As a result of the discovery of the property of superconductivity, mercury was observed to conduct an electrical current without resistance. This observed state of zero resistance and perfect diamagnetism and the nature of magnetic flux penetration into superconducting materials have continued to draw the attention of materials scientists and solid state scientists. [Pg.948]

Superconducting materials have been known since the discovery of the phenomenon of superconductivity in 1911 by Kamerlingh Onnes. They are characterized by the absence of any measurable resistivity and by their perfect diamagnetic behavior below... [Pg.401]

A perfect superconductor is a material that, when cooled below a characteristic temperature called the critical temperature, conducts electricity without any losses or any heating, and expels magnetic fields from its interior. The former property is called zero resistance, and the latter is called perfect diamagnetism. At temperatures above T, it is a normal metal, and is ordinarily not a very good conductor. For example, lead and tin become superconductors while copper and silver, which are much better conductors, do not superconduct. [Pg.4704]

The second characteristic property called perfect diamagnetism means that the superconductor material does not permit an applied magnetic field B to penetrate into its interior. Those that totally exclude the applied magnetic field are known as Type I, and they are the superconducting elements such as tin, mercury, and lead, which have the respective transition temperatures 3.7, 4.1, and 7.2K. Other superconductors called Type II are also perfect conductors of electricity, but their magnetic properties are more complex. They totally exclude magnetic fields when the applied field is low, but only partially exclude them when the applied field is larger. Thus, in... [Pg.4704]

There are two aspects to perfect diamagnetism in superconductors. The first is magnetic field exclnsion if a material in the normal state is zero field cooled (ZFC), that is, cooled below Tc to the superconducting state withont any magnetic field present, and then it is placed in an external magnetic field, the field will be excluded from the superconductor. The second aspect is magnetic field expulsion. If the same material in its normal state is placed in a magnetic field, the field will penetrate and have almost the same value inside and outside because the permeability fx is so close to the free space value fXo. If this material is then field cooled (FC), that is, cooled below E in the presence of this applied field, the field will be expelled from the material this is the Meissner effect that was mentioned earlier. [Pg.4706]

Type 1 The transition between the normal state and the superconducting state is a one-step process, and the material is either perfectly diamagnetic or not at a particular applied field. [Pg.125]

Strong diamagnetic materials exhibit a volume susceptibility close to the limit of x = — 1 (dimensionless). These obey perfect diamagnetic screening due to a superconducting current and in fact they are superconductors. Thus the measurement of magnetic susceptibility serves as a convenient and fast identification of superconductivity, even for powder materials (the Meissner effect). However, due to the considerable susceptibility value, the demagnetisation effect becomes substantial and thus a correct determination of... [Pg.346]


See other pages where Superconductivity perfect diamagnetism is mentioned: [Pg.176]    [Pg.4]    [Pg.6]    [Pg.6]    [Pg.626]    [Pg.395]    [Pg.307]    [Pg.159]    [Pg.259]    [Pg.65]    [Pg.422]    [Pg.422]    [Pg.4705]    [Pg.140]    [Pg.43]    [Pg.43]    [Pg.126]    [Pg.130]    [Pg.131]    [Pg.142]    [Pg.24]    [Pg.817]    [Pg.1206]    [Pg.42]    [Pg.4704]    [Pg.2025]    [Pg.2025]    [Pg.2082]    [Pg.1971]    [Pg.1971]    [Pg.2028]    [Pg.2191]    [Pg.2191]    [Pg.2248]    [Pg.176]    [Pg.95]   
See also in sourсe #XX -- [ Pg.115 ]




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