  The study of the hyperfine (hfs) anomaly in neutron rich nuclei can give a
very specific and unique way to study the neutron distribution and the
clustering structure. We study the sensitivity of the hfs anomaly to the
clustering effects in the 9Be isotope using two different nuclear wave
functions obtained in the three-cluster (alpha+alpha+n) model. The results are
compared to those obtained for 9,11Be in a two-body core + neutron model to
examine whether the hfs anomaly is sensitive to a halo structure in 11Be.
