Hysteresis model for polycrystalline high-<i>T</i> <i>c</i> superconductors

Abstract

The hysteresis exhibited by ceramic superconductors can be modeled using a phenomenological critical current density of the form Jc=α/(B0+B) with suitable extensions. At low temperatures (near 4 K), satisfactory results can be obtained using this form and neglecting the equilibrium magnetization. However, we show that at higher temperatures the incorporation of the equilibrium magnetization becomes more important. At 77 K, the commonly observed shape of the curves is dominated by the equilibrium magnetization. An approximate model including the equilibrium magnetization is described and compared to measurements made at 77 K.