Disappearance of 2D Magnetic Character inQuasi-1D System CoNb₂O₆ under Magnetic Field

Abstract

We report neutron scattering as well as ac susceptibility studies on the formation of magnetic ordering in a quasi-1D ferromagnetic chain system CoNb₂O₆ in magnetic fields up to 600, Oe. At T=1.5, K, a noncollinear ferrimagnetic (FR) phase with up-up-down spin arrangement along the b axis is field-induced in the magnetic field above -- 300, Oe. Interestingly, the pronounced 2D magnetic character previously found in the noncollinear antiferromagnetic phase disappears in the FR phase. This is direct evidence that the 2D magnetic character is due to the cancellation of interchain exchange fields at an apex site of a 2D isosceles-triangular lattice where quasi-1D ferromagnetic chains lie.