Effect of quenched disorder in the entropy-jump at the first-order vortex phase transition of Bi_2Sr_2CaCu_2O_{8+delta}

M. I. DOLZ; P.PEDRAZZINI; H. PASTORIZA; M. KONCZYKOWSKI; Y. FASANO

JOURNAL OF LOW TEMPERATURE PHYSICS

SPRINGER/PLENUM PUBLISHERS

Lugar: New York; Año: 2015 vol. 179 p. 28 - 34

0022-2291

We study the effect of quenched disorder in the thermodynamic magnitudes entailed in the first-order vortex phase transition of the extremely layered Bi_2Sr_2CaCu_2O_{8+delta} compound. We track the temperature-evolution of the enthalpy and the entropy-jump at the vortex solidification transition by means of AC local magnetic measurements. Quenched disorder is introduced to the pristine samples by means of heavy-ion irradiation with Pb and Xe producing a random columnar-track pins distribution with different densities (matching field B_f). In contrast with previous magneto-optical reports, we find that the first-order phase transition persists for samples with B_f up to 100 Gauss. For very low densities of quenched disorder (pristine samples), the evolution of the thermodynamic properties can be satisfactorily explained considering a negligible effect of pinning and only electromagnetic coupling between pancake vortices lying in adjacent CuO planes. This description is not satisfactory on increasing magnitude of quenched disorder.