ac losses in R EBa2Cu3O7−y superconductors

Abstract
We present the results of hysteretic ac losses of REBa2Cu3O7−y (RE=Gd, Dy, Er, Eu, Y) calculated from our magnetization data graphically at various temperatures (4.2 K≤T<Tc ) and amplitudes of sweeping field (104–4.7 T). We find that the relation of ac loss w versus amplitude of sweeping field Hm follows a power law: wHnm, where n varies from 7 to 1 in various regions of sweeping field Hm. We find that at a fixed field amplitude HmHp (Hp is the field of full penetration), the dependence of ac losses w on temperature T follows an exponential law: we−βT, which cannot be treated within a mechanism controlled by flux creep.