The Magnetic and Structural Properties of Bulk Amorphous and Crystalline Co‐P Alloys

Abstract

Abstract Bulk samples, of the order 0.2 mm thick, of cobalt‐phosphorus alloys have been prepared by prolonged electroless deposition with phosphorus contents varying from 5 to 9 at%. Alloys with less than 8.8 at% were found to be crystalline with a single‐phase h.c.p. structure, and those with 9 at% were amorphous. The saturation magnetization, magnetostriction, coercivity, and susceptibility of the crystalline alloys varied uniformly with phosphorus content. The amorphous alloys had significantly different magnetic properties from the crystalline ones of similar composition; in particular the susceptibility was nearly two orders of magnitude greater. This greater susceptibility was predominantly associated with the absence of magnetocrystalline anisotropy in the non‐crystalline material. On annealing, the amorphous material first transformed to a single‐phase h.c.p. structure similar to that of the crystalline alloys, and at a higher temperature to the equilibrium two‐phase structure of a cobalt‐rich h.c.p. phase and an orthorhombic Co 2 P phase. The susceptibility of the amorphous alloy fell by a factor of 15 times on annealing. This was attributed to the introduction of crystalline order and hence magneto‐crystalline anisotropy.