Orientation of Co2+ and Cu2+ ions introduced L-type zeolite observed with a magnetic field

Abstract

L-type zeolite with Co²⁺ and Cu²⁺ ions in 3d-transition-metal ions were prepared via ion exchange. The suspension containing these zeolite was used for slip-casting under a 12 T magnetic field applied perpendicular to the substrate surface, resulting in an orientation parallel to the c-axis for Co-L and an orientation vertical to the c-axis for Cu-L. The orientation behavior was strongly affected by the magnetocrystalline anisotropy of the L-type zeolite introduced by Co²⁺ and Cu²⁺ ions. X-ray absorption fine structure and diffuse-reflectance measurements indicated that the introduced Co²⁺ and Cu²⁺ ions formed six-coordinated hydration complexes in the zeolite structure. These hydrated complexes have a distorted octahedral structure. The results suggest that the stable direction of the magnetic moment of the hydration complex at site B of L-type zeolite depends on the strain direction. The Co²⁺ and Cu²⁺ hydration complexes have different strain directions, and the difference in orientation is speculated to be due to the different stable directions of the magnetic moment within the zeolite.