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.