Magnetic anisotropy and shape of cobalt precipitates in copper

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Abstract
Ferromagnetic single-domain coherent cobalt precipitates have been produced in copper single crystals with 1% cobalt by annealing for 20 and 40 hours at 600°C in a magnetic field of 1.15×106 A/m applied parallel to various principal crystallographic directions. Anisotropy of the coercive force obtained from magnetization curves, and anistropy of the radii of gyration obtained from neutron small-angle scattering patterns were interpreted in terms of a particle model according to which the precipitates consist of one, two or three mutually penetrating prolate ellipsoids for an annealing field parallel to [100], [011] or [111] directions respectively. The directional dependence of coercive force agrees with calculations based on the superposition of crystalline and shape anisotropy. Speculative arguments will be presented for the growth of non-spherical precipitates with various symmetries during the annealing process.