Reversible and irreversible magnetocaloric effect in the NdBa₂Cu₃O₇superconductor in relation to specific heat and magnetization

Abstract

A recently developed technique for measuring the isothermal magnetocaloric\ncoefficient ($M_T$) is applied to the study of a superconducting\nNdBa$_2$Cu$_3$O$_7$ single crystal. Results are compared with magnetization\n($M$) and specific heat ($C$). In the reversible region both $C$ and $M_T$\nfollow the scaling law of the 3D-xy universality class. The anomalies connected\nwith flux-line lattice melting are visible on $M_T(B)$ curves as peaks and\nsteps, similar to $C(T)$ curves yet with much smaller background. At lower\ntemperature, in the irreversible region the $M_T(B)$ behaviour resembles more\nthat of $M(B)$, exhibiting the "fishtail" effect. Our results confirm that the\npeculiarities of the phase diagram known from the high temperature\nsuperconductor YBa$_2$Cu$_3$O$_7$, e.g. vortex melting, dominance of critical\nfluctuations and absence of a $B_{c2}$ critical field line, are a common\nproperty of RE-123 systems.\n