Disorder in cobalt single crystals

Disorder in both allotropic phases of pure single-crystalline cobalt was studied by elastic neutron scattering in order to separate bulk from surface effects and to remove diffuse inelastic contributions. The intensity variation along 10l, measured at different temperatures, was analysed quantitatively in terms of Jagodzinski's disorder theory. The values found for the degree of disorder in the h.c.p. phase were lower than those reported before for powder samples and remain nearly unaffected when approaching the transition temperature. The f.c.c. phase is always (below and above the transition) well ordered. However, the temperature behaviour of the f.c.c. and the h.c.p. precursor regimes in the h.c.p. and the f.c.c. modifications, respectively, is different. The connection between disorder and the martensitic h.c.p.-f.c.c. transformation is discussed.