Process of magnetic field penetration into the high-temperature superconductor YBa2Cu3O7−δ

YBa2Cu3O7$minus$X flux field penetration determined by acoustic emission data

“…Substituting the AE measured current value 0.5 A into equation ( 2), the radius of the sample r 0 = 3 × 10 −3 m and taking r − r 0 as the coherence length ξ = 1.2 × 10 −9 m [9] (because the radius of a flux is approximately equal to ξ ), we have obtained H 1 to be equal to 104.0 Oe. This value of H 1 is in good agreement with H 1 = 90 Oe measured by the internal friction in [4].…”

“…On the other hand, H 1 can obviously be determined by mechanical methods. Indeed, the magnetic field penetration into YBa 2 Cu 3 O 7−X ceramic has been studied by an internal friction method [4]. It was found that a field began to penetrate into a material at H 1 = 90 Oe.…”

YBa2Cu3O7 xceramic mixed-state field detected by an acoustic emission method

“…Moreover, we have calculated H * = 480 Oe using equation (1). These observed results of H s and H * are in approximate agreement with the respective values from [4].…”

“…So it is necessary to note that the AE signals value is of the same order of magnitude as in BaTiO 3 crystals [7]. Now we compare our H s received result with one result in [4]. Our H s is so high because penetrating a magnetic field incurs the problem of grain structure.…”

“…On the other hand, the mechanics-measuring methods are free from the influence of magnetic irreversibility. Indeed, some years ago values of H C1 = 90 Oe, H * ≈ 350 Oe and H s 600 Oe were measured in YBa 2 Cu 3 O 7−x bulk ceramic samples (∼2 mm in thickness, ∼5 µm in grain size) by the internal friction method [4]. These received H C1 , H * and H s values are approximately satisfied by equation (1).…”