Absence of the anomalous second length scale in the bulk of a terbium single crystal

Recent neutron studies of the magnetic critical fluctuations in Tb show that the scattering intensity from the second length scale is strongly enhanced over a 200 μm thick region near the surface of the crystal. A fundamental question that remains, however, is whether or not this second length scale is an intrinsic property of the bulk. Using a new, much larger cube-shaped Tb crystal, we are able to mask the scattered neutron beam such that contributions form the near-surface regions never reach the detector. Under these conditions, we find no evidence of the second length scale