Antiferromagnetic ordering of Ru and Gd in superconducting RuSr 2 GdCu 2 O 8

Neutron diffraction has been used to study the magnetic order in ${\mathrm{RuSr}}_{2}{\mathrm{GdCu}}_{2}{\mathrm{O}}_{8}.$ The Ru moments order antiferromagnetically at ${T}_{N}=136(2)$ K, coincident with the previously reported onset of ferromagnetism. Neighboring spins are antiparallel in all three directions, with a low T moment of $1.18(6){\ensuremath{\mu}}_{B}$ along the c axis. Our measurements put an upper limit of $\ensuremath{\sim}0.1{\ensuremath{\mu}}_{B}$ to any net zero-field moment, with fields exceeding $0.4T$ needed to induce a measurable magnetization. The Gd ions order independently at ${T}_{N}=2.50(2)$ K with the same spin configuration.