SUPERCONDUCTIVITY AND WEAK FERROMAGNETISM IN EU1.4CE0.6RU1-XFEXSR2CU2O10-DELTA

The system Eu1.4Ce0.6Ru1-xFexSr2Cu2O10-delta with x = 0, 0.13 and 0.25 has been studied by de magnetometry to determine the superconducting and weak-ferromagnetic (W-FM) properties. Eu1.4Ce0.6RuSr2Cu2O10-delta is a magneto-superconductor with T-M(Ru)=122 and T-C=32 K thus T-M muc h greater than T-C. Superconductivity is confined to the CuO2 planes, and the magnetic ordering is due to the Ru sublattice. The effect of F e (x = 0.13 and 0.25) is: (i) to suppress SC in both compounds and (ii ) to diminish the weak-ferromagnetic (W-FM) properties (e.g. the satur ation moment (M-sat,,) and the remanent moments) of the Ru sublattice. The fast drop in M-sat,, at 5 K scales with Fe concentration. Mossbau er spectroscopy studies reveal two inequivalent Fe sites, and that in both sites, Fe does not order magnetically. This proves that the W-FM state is due to the Ru site. (C) 1997 Elsevier Science B.V.