Orthogonal spin arrangement in quasi-two-dimensional La_2Co _2O_3Se_2

摘要

The crystal, electronic, and magnetic structures of the cobalt oxyselenide La_2Co_2O_3Se_2 were investigated through powder neutron diffraction measurements and band structure calculations. This oxyselenide crystallizes in a tetragonal layered structure with space group I4/mmm. The Co ion is sixfold-coordinated by two oxide ions and four selenide ions, and the face-sharing CoO_2Se_4 octahedra form Co_2OSe_2 layers. The band structure calculations revealed that the Co ion is in the divalent high-spin state. Rietveld analysis of the neutron diffraction profiles below 200 K demonstrated that the Co moments have a noncollinear antiferromagnetic structure with the propagation vector k = (~1/_2, ~1/_2, 0). The ordered magnetic moment was determined to be 3.5μ_B at 10 K, and the directions of the nearest-neighbor Co moments are orthogonal each other in the c plane.