Spin density wave magnetism in copper—manganese alloys

The incommensurate magnetization waves (IMW) occuring at the wave vector Q = (1, 0.5 − δ, 0) 2π a and equivalent positions in reciprocal space in Cu 1− x Mn x have been studied as a function of temperature, wavevector, frequency and composition, using high-resolution, unpolarized neutron scattering techniques. We find that the elastic component of the scattering cross section at these incommensurate wavevectors approaches zero in the vicinity of the “spin glass” freezing temperature, T f , closely resembling that expected for an order parameter on approach to the critical point. We suggest that the interaction between Mn atoms is long-range and intimately connected to a spin density wave instability.