The partially disordered state of the frustrated face-centred cubic antiferromagnet GdInCu4

The magnetic structure of the frustrated fee antiferromagnet GdInCu4 was in vestigated by measuring the magnetic susceptibility, Gd-155 Mossbauer effec t and neutron diffraction. We propose a partially disordered structure of t ype III (Q = (0 1/2 1)), in which only the Gd atoms in every second (010) l ayer are ordered and the remaining half of the atoms sandwiched by the stat ic layers fluctuate dynamically just below T-N and slow down to exhibit gla ss-like freezing of the layers at lower temperatures. This partially disord ered state is the first example found for the fee lattice which is driven n ot by the moment instability but by the dynamical (entropy) effect.