Theory of Adiabatic Nuclear Magnetic Ordering in Cu

The phase diagram for the nuclear magnetic ordering of Cu in a magnetic field is theoretically found to exhibit three distinct phases in accordance with recent measurements. It is a consequence of the frustrated ground-state properties of an antiferromagnetic fcc structure with nearest-neighbor Heisenberg and dipolar interactions, a model also of relevance for the resonating-valence-bond problem. The adiabatic process is discussed, and nonadiabaticity caused by off-diagonal spin-spin interactions in the ordered, canted phase is found to be in accordance with the experimental value.