THE MAGNETIC-STRUCTURE OF KNIASO4 - A 2-DIMENSIONAL HONEYCOMB LATTICE

The magnetic structure of KNiAsO4, an example of a two-dimensional hon eycomb lattice, has been determined from neutron powder diffraction da ta collected at 1.5 and 30 K. The crystallographic unit cell (R3) is d oubled along a (k = 1/2, 0, 0) and the three observed magnetic reflect ions are indexed as 101, -102, 104 in the extended cell. The magnetic structure can be described as zig-zag antiferromagnetic chains paralle l to a such that each moment has one nearest neighbor parallel and two antiparallel. This contrasts with the structurally related BaNi2(AsO4 )2, in which each magnetic ion has one antiparallel and two parallel n eighbors. (C) 1994 Academic Press, Inc.