The magnetic behaviour in heterogeneous f.C.C. co₁₀cu₉₀melt-spun ribbons

The metastable magnetic alloy Co₁₀Cu₉₀has been prepared by the conventional melt-spinning technique. The rapid solidification process results in an extended solubility of Co in Cu although some Co particles already have precipitated during quenching. In comparison with conventional ageing methods, Joule heating could also be adopted to fabricate granular Co-Cu alloys with even finer Co particles. The finest size of 4.0nm has been achieved for Co₁₀Cu₉₀alloy after annealing with a current I = 4 A for 1 rnin. Single-domain behaviour results in a value of coercivity in excess of 40.0 kAm^-1for the sample annealed with I = 9.5 A. Below the size of 6.0 nm, Co particles exhibit superparamagnetic behaviour at room temperature, which has been investigated using a superconducting quantum interference device magnetometer. A unique change in M_swith annealing current or temperature was discovered.