Study on the Microstructure and Magnetic Properties of Nd-Fe-B/Fe-Co Composite Nanowires

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.