Magnetization curves and hysteretic losses in superconducting films with edge barrier

Abstract

The influence of both bulk and edge pinning on the response of a thin-film superconductor to an oscillating magnetic field is considered. The magnetic-flux-defreezing field and the flux-exit field are defined. The hysteresis and magnetization curves of a sample are constructed for the entire cycle of the magnetic field. From this, we obtain the dependence of the hysteresis losses on the field amplitude.

Field-dependent critical current in type-II superconducting strips: Combined effect of bulk pinning and geometrical edge barrier

“…1, the left and right boundaries of the vortex dome a ′ and b ′ are determined by simultaneously solving Eqs. (9) and (12); Eq. (12) also gives the condition that dK z (x)/dx = 0 at x = a.…”

“…To determine the critical current with domes present, one must first calculate the vortex (and antivortex) density n(x) = µ 0 H y (x, 0)/φ 0 inside the dome, where K z (x) = K p , and the sheet current density K z (x) outside, where n(x) = 0. We have obtained these mathematically by using the Cauchy integral inversion method 2,4,7,9,20 to invert the Biot-Savart law. However, we shall use the method of complex fields 21 to give a physical interpretation of the mathematical results.…”

“…The combination of a geometrical edge barrier and bulk pinning recently has been shown to strongly affect the properties of low-dimensional superconductors (thin films, single crystals, and tapes with high demagnetizing factors) placed in either a perpendicular magnetic field [1][2][3][4][5] or a transport-current-carrying state [6][7][8][9] . While most experimental studies of the field dependence of the critical current I c are being interpreted solely on the basis of bulk-pinning theory (see for example [10][11][12][13][14] ), a number of works 6,8,15,16 have shown that a geometrical edge barrier (or surface barrier) may strongly affect I c .…”

Magnetic-field dependence of the critical currents in a periodic coplanar array of narrow superconducting strips

“…The critical current is known to depend upon both local pinning centers in the material and the shape of the conductor's cross section. Even in the absence of bulk pinning, isolated type-II superconducting thin-film strips subjected to perpendicular magnetic fields show magnetic hysteresis due to geometrical edge barriers [2,3,4,5,6,7]. Such strips have finite critical currents arising from the edge barriers [8].…”

“…To calculate the combined effects of geometrical barriers and bulk pinning is more difficult, but this has been accomplished for single strips in [4,5,7,15,16,17,18,19], and a theoretical analysis of the magnetic-field dependence of the critical current of an isolated superconducting strip due to both an edge barrier and uniform bulk pinning has been presented in [20]. Here we extend the above calculations to account for both geometrical edge barriers and bulk pinning in an infinite number of strips using the X-array method [21], by which the magnetic-field and current-density distributions for an array of parallel superconducting strips arranged periodically along the x axis in the plane y = 0 can be obtained analytically from the solutions for an isolated superconducting strip [20].…”