MOMENT CLOUDS IN CUMN

Advantage was taken of the high magnetic susceptibility of Cu-Mn alloy s in the range 12 to 22 at. % Mn to observe field-dependent magnetic n eutron scattering from a single crystal containing 21.3 at. % Mn. The scattering was measured with unpolarized neutrons at low angles and be tween the (1,0,0) and (1,1/2,0) positions in reciprocal space using a neutron energy of 14.8 MeV. The magnetic scattering was approximately uniformly reduced by about 10% at 4.2 K after warming above the glass temperature and cooling again to 4.2 K in a field of 4.25 T. Reduction of the intensity of all magnetic features by the application of the f ield indicates that all the magnetic periodicities are intimately conn ected to the uniform magnetic response. A model which assumes that the alloy contains entities with both a ferromagnetic moment associated w ith the (0,0,0) scattering and an antiferromagnetic periodicity associ ated with the (1,1/2-delta,0) scattering yields a ferromagnetic moment for the entity of 36 mu(B) estimated from the reduction in scattering . This compares with 42 mu(B) estimated from the intensity and width o f the low angle. scattering.