To solve the problem of the low coercivity of Nd-Fe-B-based nanowires impeding their application in magnetic storage media, highly ordered Nd-Fe-B/Fe-Co composite nanowires were fabricated in an anodic alumina template by means of the alternating electrochemical deposition method. In this paper, the effect of soft and hard magnetic phase compositing on the magnetic properties of Nd-Fe-B-based nanowires was investigated, and the coercivity improvement mechanism was demonstrated. The results show that after annealing at 600 °C for 2 h, Nd-Fe-B/Fe-Co nanowires crystallize into a multiphase structure containing a hard Nd2(Fe, Co)14B phase and soft NdB4, NdB6, Fe7Nd, and Fe7Co3 phases. It is characterized that the Nd2(Fe, Co)14B phase preferentially nucleates, followed by NdB4 + NdB6 + Fe7Nd, while Fe7Co3 has been formed in as-deposited nanowires. The existence of a Nd2(Fe, Co)14B phase with high anisotropy fields, the remanence enhancement effect produced by exchange coupling between hard-soft magnetic phases, and the pinning effect between different phases make the composite nanowires approximately exhibit single hard magnetic phase characteristics with coercivity and remanence ratio as high as 4203.25 Oe and 0.89. The results indicate that synthesizing Nd-Fe-B/Fe-Co exchange-coupled composite nanowires via alternating electrodeposition is an effective way to optimize the magnetic performance of Nd-Fe-B-based nanowires.
Keywords: Fe-Co; Nd-Fe-B; electrochemical deposition; exchange coupling; magnetic properties.