Characteristic crossing point (T* ≈ 2.7 K) in specific heat curves of samples RuSr2Gd1.5Ce0.5Cu2O10-δ taken for different values of magnetic field

Magnetic properties of polycrystalline samples of RuSr2(Gd1.5Ce0.5)Cu2O10-delta, as-prepared (by solid-state reaction) and annealed (12 h at 845 degrees C) in pure oxygen at different pressure (30, 62 and 78 atm) are presented. The specific heat and magnetization were investigated in the temperature range 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 at T approximate to 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 S-8(7/2) of paramagnetic Gd3+ 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-* approximate to 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 field H-* approximate to 3.7 T. These effects can be considered as a manifestation of the crossing point phenomenon which is supposed to be inherent for strongly correlated electron systems.