Atomic ordering in A15-type phases in the vanadium--nickel and vanadium--cobalt systems

Atomic ordering in the V–Ni and V–Co A 15-type phases has been studied using neutron diffraction. The V–Ni structure is shown to be ordered to the maximum extent permitted by the ``off stoichiometric'' composition, V77.5Ni22.5. The V–Co structure possessing the ``ideal'' composition V75.0Co25.0 is also highly ordered. However, the V–Co diffraction data are less accurate due to neutron absorption by the cobalt atoms and interference from the sample holder. No magnetic structures were detected in the V–Co phase at 4.2 °K.