Reversible and irreversible magnetocaloric effect in theNdBa2Cu3O7 superconductor in relation to specific heat and magnetization

Abstract

A recently developed technique for measuring the isothermal magnetocaloric coefficient(MT) is applied to the studyof a superconducting NdBa2Cu3O7 single crystal. Results are compared with magnetization(M) and specific heat(C). In the reversibleregion both C and MT follow the scaling law of the 3D-xy universality class. Theanomalies connected with flux-line lattice melting are visible onMT(B) curves as peaks andsteps, similar to C(T) curves yet with much smaller background. At lower temperature, in the irreversible region theMT(B) behaviour resemblesmore that of M(B), exhibiting the ‘fishtail’ effect. Our results confirm that the peculiaritiesof the phase diagram known from the high-temperature superconductorYBa2Cu3O7, e.g. vortex melting, dominance of critical fluctuations and absence of aBc2 critical field line, are a common property of RE-123 systems.