Magnetic structure and orbital state ofCa3Ru2O7investigated by resonant x-ray diffraction

Abstract

Resonant x-ray diffraction at the L 2-and L 3-absorption edges of Ru has been used to investigate the magnetic structure of Ca 3 Ru 2 O 7 , a material with a bilayer perovskite structure that undergoes a transition from a high-temperature metallic to a low-temperature insulating phase at 48 K. In the insulating phase, magnetic Bragg reflections characteristic of A-type antiferromagnetic order ͑that is, ferromagnetic RuO 2 bilayers coupled antiferromagnetically along the c-axis͒ were identified. The azimuthal-angle dependence of the diffracted intensity implies that the magnetic moments are aligned along the b-axis in the RuO 2 planes. In the metallic phase, the A-type magnetic order persists up to the Néel temperature of 56 K, but the sublattice magnetization decreases by a factor of ϳ1.7 and rotates by 90°within the planes. Resonant signals characteristic of uniform or staggered orbital order were not found within the experimental sensitivity, probably reflecting a weak orbital polarization in the insulating state.

Field-induced orbital patterns in ferromagnetic layered ruthenates

“…Numerical calculations on a 2 ϫ 2 cluster and of a cluster embedded in a periodic environment reveal that the competing effects driven by orbital exchange and crystal field put the system on the verge of a FO/AFO behavior, a circumstance that makes the character of OO in absence of an applied field quite elusive. This outcome may be supported by recent resonant x-ray scattering measurements on Ca 3 Ru 2 O 7 , 39 where no appreciable signal of staggered FO or AFO is found within experimental resolution. We argue that this feature is at the origin of the soft behavior and the easy field tunability of the OO phases.…”

Interplay between the lattice and spin degrees of freedom in(Sr1−xCax)3Jin1, Qu2, Qian3 et al. 2010Phys. Rev. B264280View full textAdd to dashboardCite

“…For Ca 3 Ru 2 O 7 , different M-H curves are observed between H ʈ a and H ʈ b while a spin-flop transition occurs at ϳ6 T for H ʈ b, M͑H͒ for H ʈ a is small and almost linear as a function of field up to 7 T. This indicates that the b axis is the easy axis of spin polarization. 43,44 With Sr substitution for Ca, the anisotropy between H ʈ a and H ʈ b decreases. For the sample with x = 0.8, although the spin-flop transition still only occurs for H ʈ b, the magnetization for H ʈ a is larger than that of the x = 1 sample.…”

Spin polarization of Ru in superconducting Ba(Fe0.795Ru0.205)2As

“…33,38 In Ca 2 RuO 4 , both orbital and magnetic order are present and the orbital ordering emerges at higher temperature than the magnetic ordering temperature; the two resonant peaks at the Ru L edges are temperature dependent, changing both the spectral weights and positions, because of the different resonant responses from the orbital and the magnetic order. 33 Ca 3 Ru 2 O 7 has been also claimed to display an orbital ordering, but that has not yet been confirmed.…”