The role of bulk pinning in the Clem valley in hysteresis losses in type II superconductors

Measurements of hysteresis losses W(h0, Hb) at several fixed amplitudes h0 versus a static bias magnetic field Hb collinear to h0 and directed along the length or the width of a VTi ribbon which exhibits significant magnetic anisotropy, are reported and are very well reproduced exploiting bulk pinning alone hence neglecting equilibrium diamagnetism and surface barriers. Families of curves of D≡W(h0, Hb)/W(h0,0) vs z≡Hb/h0 at various fixed h0 were calculated for planar and cylindrical geometry, neglecting surface steps, using the simple formulas μ0 jc=dB/dx=α/B, α/B0.5, α/B0.1, α[1−(B/Bc2)], and α/(B+Δ) for the bulk critical current density. For slab geometry and the first four functions listed, the curves of D vs z are independent of h0/H* when h0