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

TL;DR

This study applies a novel measurement technique to analyze the magnetocaloric effect in NdBa2Cu3O7 superconductors, revealing reversible and irreversible behaviors linked to flux-line lattice melting and critical fluctuations, consistent with high-temperature superconductor properties.

Contribution

It introduces a new application of the isothermal magnetocaloric coefficient measurement to NdBa2Cu3O7, connecting magnetocaloric, magnetization, and specific heat data to superconducting phase transitions.

Findings

Scaling law of 3D-xy universality class observed in reversible region

Flux-line lattice melting anomalies detected in M_T(B) curves

Irreversible region shows fishtail effect similar to magnetization

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 $B_{c2}$ critical field line, are a common property of RE-123 systems.