Characteristic crossing point ($T_{\ast}\approx 2.7$ K) in specific-heat curves of samples RuSr$_2$Gd$_{1.5}$Ce$_{0.5}$Cu$_2$O$_{10-\delta}$ taken for different values of magnetic field

TL;DR

This study investigates the specific heat and magnetic properties of RuSr$_2$(Gd$_{1.5}$Ce$_{0.5}$)Cu$_{2}$O$_{10- ext{delta}}$ samples, revealing a characteristic crossing point in specific heat curves at 2.7 K across different magnetic fields, indicating a universal feature of strongly correlated systems.

Contribution

It reports the observation of a universal crossing point in specific heat curves of a complex cuprate, linking it to the crossing-point phenomenon in strongly correlated electron systems.

Findings

Specific heat shows a jump at 37.5 K indicating superconductivity.

A Schottky anomaly appears below 20 K due to Gd$^{3+}$ ions.

Crossing points in $C(T)$ and $C(H)$ curves are observed at 2.7 K and 3.7 T, respectively.

Abstract

Magnetic properties of polycrystalline samples of RuSr$_2$(Gd$_{1.5}$Ce$_{0.5}$)Cu$_{2}$O$_{10-\delta}$, as-prepared (by solid-state reaction) and annealed (12 hours at 845$^{\circ}$C) in pure oxygen at different pressure (30, 62 and 78 atm) are presented. Specific heat and magnetization were investigated in the temperature range 1.8--300 K with a magnetic field up to 8 T. Specific heat, $C(T)$, shows a jump at the superconducting transition (with onset at $T\approx 37.5$ K). Below 20 K, a Schottky-type anomaly becomes apparent in $C(T)$. This low-temperature anomaly can be attributed to splitting of the ground term ${^8}S_{7/2}$ of paramagnetic Gd$^{3+}$ ions by internal and external magnetic fields. It is found that curves $C(T)$ taken for different values of magnetic field have the same crossing point (at $T_{\ast}\approx 2.7$ K) for all samples studied. At the same time, $C(H)$ curves taken for different temperatures have a crossing point at a characteristic field $H_{\ast}\approx 3.7$ T. These effects can be considered as manifestation of the crossing-point phenomenon which is supposed to be inherent for strongly correlated electron systems.