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$_{10-δ}$ taken for different values of magnetic field

B. I. Belevtsev; V. B. Krasovitsky; D. G. Naugle; K. D. D. Rathnayaka; G. Agnolet; I. Felner

doi:10.1088/0953-8984/21/45/455602

paper

Characteristic crossing point ( $T_{*} \approx 2.7$ K) in specific-heat curves of samples RuSr $_{2}$ Gd $_{1.5}$ Ce $_{0.5}$ Cu $_{2}$ O $_{10 - δ}$ taken for different values of magnetic field

arXiv:0910.2384 · doi:10.1088/0953-8984/21/45/455602

Abstract

Magnetic properties of polycrystalline samples of RuSr $_{2}$ (Gd $_{1.5}$ Ce $_{0.5}$ )Cu $_{2}$ O $_{10 - δ}$ , 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 $T_{*} \approx 2.7$ K) for all samples studied. At the same time, $C (H)$ curves taken for different temperatures have a crossing point at a characteristic field $H_{*} \approx 3.7$ T. These effects can be considered as manifestation of the crossing-point phenomenon which is supposed to be inherent for strongly correlated electron systems.

arXiv comment10 pages, 7 figures, submitted to J. Phys.: Condens. Matter

Characteristic crossing point ( $T_{*} \approx 2.7$ K) in specific-heat curves of samples RuSr $_{2}$ Gd $_{1.5}$ Ce $_{0.5}$ Cu $_{2}$ O $_{10 - δ}$ taken for different values of magnetic field

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Characteristic crossing point (T∗​≈2.7 K) in specific-heat curves of samples RuSr2​Gd1.5​Ce0.5​Cu2​O10−δ​ taken for different values of magnetic field

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Characteristic crossing point ( $T_{*} \approx 2.7$ K) in specific-heat curves of samples RuSr $_{2}$ Gd $_{1.5}$ Ce $_{0.5}$ Cu $_{2}$ O $_{10 - δ}$ taken for different values of magnetic field