REVERSIBLE EFFECT OF HYDROGEN ON SUPERCONDUCTIVITY AND WEAK FERROMAGNETISM IN EU1.4CE0.6MSR2CU2O10-DELTA (M=NB AND RU)

We have investigated the superconducting compounds Eu1.4Ce0.6MSr2Cu2O1 0-delta (M=Nb and Ru) (T-c=22 and 32 K, respectively), as well as thes e materials charged with hydrogen, by several complementary experiment al techniques. Eu1.4Ce0.6RuSr2Cu2O10-delta is magnetically ordered at T-N=122 K, thus T-N much greater than T-c. Superconductivity (SC) is c onfined to the CuO2 planes, and the magnetic ordering is due to the Ru sublattice. Among many interesting features, irreversibility phenomen a at low magnetic fields and a magnetic spin reorientation transition, which are observed, originate from antisymmetric exchange coupling of the Dzyaloshinsky-Moria type. The effect of hydrogen (0.35 at. %) is to suppress SC in both compounds and to enhance the weak-ferromagnetic properties of the Ru sublattice (T-N=225 K). In contrast to other hig h-T-c materials, this effect is reversible: namely, by depletion of hy drogen, SC is restored in both materials and for M=Ru, the T-N drops b ack to 122 K.