The x = 0 parent compound of the Ca2+xY2-xCu5O10 family of quasi-one-dimens
ional copper oxides was investigated by neutron powder diffraction. Long ra
nge antiferromagnetic order, with ferromagnetic alignment of the moments al
ong the copper oxide chains, was observed below T-N = 29.5 K. The low tempe
rature ordered moment is 0.92 mu(B), close to the free ion value. The resul
ts are compared to observations on other magnetically ordered copper oxides
. [S0163-1829(99)09609-5].