Reversible and irreversible magnetocaloric effect in the NdBa_2Cu_3O_7 superconductor in relation with specific heat and magnetization

T. Plackowski; Y. Wang; R. Lortz; A. Junod; Th. Wolf

doi:10.1088/0953-8984/17/43/007

paper

Reversible and irreversible magnetocaloric effect in the NdBa_2Cu_3O_7 superconductor in relation with specific heat and magnetization

arXiv:cond-mat/0502326 · doi:10.1088/0953-8984/17/43/007

Abstract

A recently developed technique for measuring the isothermal magnetocaloric coefficient ( $M_{T}$ ) is applied to the study of a superconducting NdBa $_{2}$ Cu $_{3}$ O $_{7}$ single crystal. Results are compared with magnetization ( $M$ ) and specific heat ( $C$ ). In the reversible region both $C$ and $M_{T}$ follow the scaling law of the 3D-xy universality class. The anomalies connected with flux-line lattice melting are visible on $M_{T} (B)$ curves as peaks and steps, similar to $C (T)$ curves yet with much smaller background. At lower temperature, in the irreversible region the $M_{T} (B)$ behaviour resembles more that of $M (B)$ , exhibiting the "fishtail" effect. Our results confirm that the peculiarities of the phase diagram known from the high temperature superconductor YBa $_{2}$ Cu $_{3}$ O $_{7}$ , e.g. vortex melting, dominance of critical fluctuations and absence of a $B_{c 2}$ critical field line, are a common property of RE-123 systems.

18 pages, 12 figures