Magnetic ordering in the superconducting weak ferromagnets RuSr2GdCu2O8 and RuSr2EuCu2O8 -: art. no. 054440

Neutron powder-diffraction measurements for RuSr2GdCu2O8 and RuSr2EuCu2O8 show that both compounds, below their magnetic ordering temperatures of 133 and 120 K, respectively, have the same G-type antiferromagnetic structure in which Ru moments are antiparallel in all three crystallographic directions. The ferromagnetism in these compounds, which is clearly indicated by hysteresis loops, can be explained if the Ru moments are canted to give a net moment perpendicular to the c axis. In such a model, one would expect an induced ferromagnetic ordering of the magnetic Gd ions, which have large (similar to 7 mu (B)) moments, as a result of the net field at the Gd site, while Eu, being nonmagnetic, would exhibit no such response. The dramatically larger hysteresis loops for RuSr2GdCu2O8 compared to those for RuSr2EuCu2O8 are consistent with this hypothesis.