Magnetic order and fluctuations in superconducting UPt sub 3.

Neutron diffraction shows that superconducting UPt sub 3 can be an antiferromagnet with an ordered moment of micron B and a Neel temperature (T sub N) of 5K. The squared order parameter is a linear function of temperature from T sub N to the superconducting transition temperature, T sub c = 0.5K, below which it ceases to evolve. Inelastic neutron scattering demonstrates that the fluctuating moments are strongly correlated; the characteristic energy for fluctuations with wavevectors close to the ordering wavevector is 0.2meV ~ 4kT sub c.