Superposition of currents in hard superconductors placed into crossed ac and dc magnetic fields

Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

“…the magnitude of the critical current density J c , being the only parameter used within the isotropic Bean's model, is substituted by a symmetrical tensor (J c ) ik with principal values J c and J c⊥ , corresponding to the directions along and across the local magnetic induction B. In good agreement with the experiment on YBa 2 Cu 3 O 7−δ samples [1,17], the elliptic criticalstate model predicts the quasisymmetrical suppression of the average magnetization < M z >, for paramagnetic and diamagnetic initial states, by sweeping a transverse field H y of magnitude much smaller than dc-bias magnetic field H z [19,22]. When the magnitudes of the crossed fields H y and H z are comparable, the value of the magnetization < M z > after many cycles of the transverse field H y turns out to be positive for both diamagnetic and paramagnetic initial states if J c > J c⊥ .…”

“…The discovery of the phenomenon known as quasisymmetrical collapse of magnetization [1], which is observed in superconductors subjected to crossed magnetic fields and well interpreted within the simple Bean's critical-state model [2,3], has been a turning point in the understanding of the magnetic behavior of hard (irreversible type-II) superconductors. Until then, the generalized double critical-state model (GD-CSM) [4,5,6,7,8], which is based on fundamental physical concepts such as flux transport and fluxline-cutting [9,10], was successfully employed to explain a variety of experiments where flux cutting occurs [11,12,13,14,15,16].…”

The Numerical Modeling and Measurement of Demagnetization Effect in Bulk YBCO Superconductors Subjected to Transverse Field

“…In spite of having been investigated for more than three decades, the subject remains a very intriguing topic for which many experimental facts are still far from being understood. In particular, we need to know whether large numbers of cycles of the crossed field lead eventually to total demagnetization, as suggested by some experiments and theories [3], or the decay of the magnetization ceases at a useful value as predicted by theories based on the critical state model [4], [5]. In this paper, a melt-textured YBCO bulk sample was magnetized along the axial direction and after that a transverse field perpendicular to the central axis applied.…”

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

“…Moreover, the interest in crossed fields has been revived with the increasing potential of singledomain bulk melt-processed R-Ba-Cu-O ͓͑R͒BCO, where R denotes a rare-earth ion͔ to trap significant magnetic fields, 5 which gives rise to the possibility of high-field permanentmagnet-like devices. 6,7 Applying a magnetic field in a direction transverse to that of the premagnetization in a bulk superconductor may cause significant decay of the trapped field, [8][9][10][11][12][13][14][15][16][17][18] which could result in the failure of such devices in practical applications. The behavior of bulk high-temperature superconductors ͑HTSs͒ in the crossed-field configuration is therefore of practical relevance as well as of fundamental academic interest.…”

“…Similar effects were observed in high-T c superconductors, initially for cylindrical Y-Ba-Cu-O carrying a transport current and subjected to a magnetic field parallel to the cylinder axis 20 and subsequently in high-T c superconductors of various shapes and microstructures. [8][9][10][11][12][13][14][15][16][17][18]21 It is now well established experimentally that the magnetization M z of a type-II superconductor sample placed in an external dc magnetic field H z is decreased strongly by applying a magnetic field H y perpendicular to both M z and H z . This behavior is known as collapse of the magnetic moment.…”