Characteristic crossing point (T*≈2.7 K) in specific heat curves of samplesRuSr2Gd1.5Ce0.5Cu2O10−δ taken for different values of magnetic field

Abstract

Magnetic properties of polycrystalline samples ofRuSr2(Gd1.5Ce0.5)Cu2O10−δ, as-prepared (by solid-state reaction) and annealed (12 h at845 °C) in pure oxygen at different pressure (30, 62 and 78 atm) are presented.The specific heat and magnetization were investigated in the temperaturerange 1.8–300 K with a magnetic field up to 8 T. The specific heat,C(T), shows a jump at the superconducting transition (with an onset atT≈37.5 K). Below 20 K, a Schottky-type anomaly becomes apparent inC(T). This low-temperature anomaly can be attributed to splitting of the ground term 8S7/2 ofparamagnetic Gd3+ ions by internal and external magnetic fields. It is found that curvesC(T) taken for different values of magnetic field have the same crossing point (atT*≈2.7 K) for all the samples studied. At the same time,C(H) curves taken for different temperatures have a crossing point at a characteristic fieldH*≈3.7 T. These effects can be considered as a manifestation of the crossing point phenomenonwhich is supposed to be inherent for strongly correlated electron systems.