The magnetic order in a single-crystal Sr2.5Ca11.5Cu24O41 (Ca11.5) was inve
stigated by Cu nuclear magnetic and quadrupole resonance (NMR\NQR) techniqu
es. The magnetic order was found to be three-dimensional (3D). Small moment
s similar to 0.02 mu(B), art: spontaneously ordered on the ladders. Dissoci
ation of hole pairs into single holes which localize below T-L similar to 6
0 K is responsible for the manifestation of the spin degree of freedom on t
he ladders. (C) 2000 Elsevier Science B.V. All rights reserved.