Field-induced thermally-activated dissipation and lock-in transition ina (YBCO)24/(PrBCO)2 multilayer thin film

Abstract

We have measured the temperature dependence of the resistivityρ of an epitaxial (YBa2Cu3O7-δ)24/(PrBa2Cu3O7-δ)2multilayer nanometre film at several magnetic fields parallel to the c-axisand at a constant magnetic field H = 4 T. The measurements were taken for various angles α betweenthe magnetic field and the surface of the film with H in the plane betweenthe measuring current I and the c-axis, and for various angles θbetween the magnetic field H and the surface of the film (ab-plane) withH ⊥ I. The resistive broadening depends mainly on the effective appliedmagnetic field He = H×(sin2θ + cos2θ/γ2)1/2 with respect to the c-axis, and shows a three-dimensionalanisotropic behaviour, where γ is the anisotropy parameter. Theangular dependences of the peak temperature Tp and the activationenergy Ue for angle θ and α>5° are in agreement withthe effective mass model, namely Tp(0)-Tp(H,θ) ∝(sin2θ + cos2θ/γ2)1/2n and Ue∝He-mwith γ = 10, n = 1.31 and m = 0.87. The dissipative resistivity belowTp for various magnetic fields can be scaled onto a single curve bythermally activated flux motion. When the applied field tilts the CuO2plane, the angular dependences of Tp and Ue reveal a lock-in transition,showing that the flux lines were trapped in the non-superconducting PrBCOlayers.