Structural, Magnetic, and Electrical Behavior of Low Dimensional Ba₂CoO₄

Abstract

The cobaltite Ba2CoO4 presents a monoclinic symmetry (space group P21 /n) and lattice parameters a = 5.891 31(7), b = 7.59 74(3), c = 10.3638(2) Å, and β = 91.90(1)°. As determined from X-ray and neutron diffraction data, its structure can be described as formed by isolated CoO4 tetrahedra defining zigzag rows running along the a axis, separated by Ba atoms in both the b and the c directions. The cobalt atoms are in a high spin Co4+ ground state, and their magnetic structure evidences the existence of antiferromagnetic and ferromagnetic alignments of the magnetic moments alternating along each of the aforementioned rows. Transport properties are related to p-type carriers.

Single Crystal Growth and Magnetic Properties of High Oxidation State Material Ba2CoO4

“…The structural information obtained within a crystal structure refinement is listed in Table . Our results are consistent with literature values . In Ba 2 CoO 4 the Co‐ions are tetrahedrally surrounded by the oxygen ions and the CoO 4 tetrahedra are separated by the Ba ions, that is, the Ba ions are octahedrally coordinated by the CoO 4 tetrahedra.…”

“…On the other hand Co 4+ ‐ions in the LS state were found in BaCoO 3 . Finally, a Co 4+ HS has been reported for Ba 2 CoO 4 with tetrahedrally coordinated Co 4+ ions . However, so far the study of its electronic and magnetic properties was limited to studies on polycrystalline samples and very small single crystals …”

“…This observation indicates an anti‐ferromagnetic structure with moments pointing in a ‐direction. However, a different magnetic structure was derived from neutron scattering experiments, which reported magnetic moments of 3.08 µ B per Co ion in c ‐direction and 0.91 µ B in b ‐direction within a noncollinear antiferromagnetic structure with propagation vector k = (1/2 0 1/2) . Also µ SR experiments provide conflictive results and indicate magnetic moments within the ab ‐plane …”

Material Synthesis and Characterization on Low-Dimensional Cobaltates

“…However, there is no associated structural transition from room temperature to 4 K [124]. We measured the temperature dependence of lattice constants (a and c) in the scat-tering plane.…”

“…This low energy excitation is slightly broadened at the zone center. Work by Boulahya et al [124] suggests that the spins are mostly aligned antiferromagnetically along the c axis with canting out of the ac plane. Their work was primarily based on an elastic neutron scattering experiment with a powder sample.…”