Spontaneous long range antiferromagnetic order in the spin-1/2 system
of silver nuclei has been observed by neutron diffraction on a single
crystal of Ag-109. Th, observed antiferromagnetic state had a simple 1
-k structure and no field induced phase transitions within the ordered
state could be indentified. Spin dependent neutron absorption was uti
lized to determine the nuclear susceptibility and entropy.