Am. Buckley et al., THE MAGNETIC-PROPERTIES AND STRUCTURES OF THE TRANSITION-METAL PYROARSENATES M(2)AS(2)O(7) (M=NI, CO, MN), Journal of solid state chemistry, 115(1), 1995, pp. 229-235
The bulk magnetic properties and magnetic structures of the pyroarsena
tes M(2)As(2)O(7) (M = Ni, Co, Mn), whose crystal structures are relat
ed to thortveitite Sc2Si2O7 have been investigated by susceptibility (
chi) measurements and neutron powder diffraction. All three compounds
behave as three-dimensional antiferromagnets. The Weiss constants thet
a are -92(1), -49(1), and -28(1) K, and the T(N)determined from the ma
xima in d(chi)/dT are 29.1(1), 11.63(5), and 8.5(1) K, respectively. I
n each case, four magnetic reflections were identified in the neutron
diffraction profiles below TN The magnetic structure of Ni2As2O7 was r
efined on the basis of an approximate low-temperature crystal structur
e. The moments make an angle of similar to 30 degrees to the c-axis in
the ac-plane. Each moment has three antiparallel nearest neighbors. T
he antiferromagnetic sheets are further stacked in antiferromagnetic s
equence along c. Comparison is made with the magnetic structure of Mn2
P2O7. (C) l995 Academic Press, Inc.