Identification of the muon stopping sites in GdSr2Cu2RuO8: Confirmation of ferromagnetic cuprate planes in a superconducting cuprate

Muon spin rotation experiments on superconducting GdSr2Cu2RuO8 reported a magnetic induction of 720–740 G. Neutron diffraction studies have shown that the Ru spins are ordered antiferromagnetically along the c-axis, while the cuprate planes are ordered ferromagnetically in the a–b plane and are stacked antiferromagnetically. Using this spin configuration with refined spin moments, we have calculated the magnetic induction at potential muon stopping sites; muons stopping in the center of the ferromagnetic CuO2 planes will experience an induction of ∼725 G, a result in excellent agreement with experiment. We predict that muon experiments, carried out at temperatures below the Gd antiferromagnetic ordering temperature, will detect an induction exceeding 1 T at one of the muon sites.