NEUTRON-DIFFRACTION DETERMINATION OF THE NUCLEAR-SPIN ORDERING IN CU AND AG AT NANO-K AND SUBNANO-K TEMPERATURES

The spontaneous nuclear spin ordering in the simple diamagnetic metals Cu and Ag has been studied by neutron diffraction using the spin depe ndent part of the nuclear cross section. Simple antiferromagnetic orde ring of type I has been found in zero field for these fcc-systems belo w 60 and 560 pK for Cu and Ag, respectively. The ordering in an applie d field has been investigated and the phase diagrams have been determi ned: a very complex phase diagram with different magnetic structures, strong hysteresis, and time dependence was found for Cu, while in Ag t he phase diagram is very simple. Comparison with ab initio calculation s allows a rather deep insight into the interactions leading to the or dering. (C) 1996 American Institute of Physics.