  We present measurements of the temperature and field dependencies of the
magnetization M(T,H) of Nd(O0.89F0.11)FeAs at fields up to 33T, which show that
superconductivity with the critical temperature Tc ~ 51K cannot coexist with
antiferromagnetic ordering. Although M(T,H) at 55 < T < 140K exhibits a clear
Curie-Weiss temperature dependence corresponding to the Neel temperature TN ~
11-12K, the behavior of M(T,H) below Tc is only consistent with either
paramagnetism of weakly interacting magnetic moments or a spin glass state. We
suggest that the anomalous magnetic behavior of an unusual high-field
paramagnetic superconductor Nd(O1-xFx)FeAs is mostly determined by the magnetic
Nd ions.
