The high cost of CoFe alloys has prevented their widespread use regardless of their promising properties: high magnetisation, high Curie temperature, as soft magnetic materials for high temperature applications. Our research has shown that the additional of AlMn can be used to create CoFeMnAl alloys, which have reduced Co content but similar saturation magnetisation as CoFe alloys, therefore providing a more economical alternative to pure CoFe soft magnets. The research studied how the addition of Al to CoFeMn0.5 changed the alloy phases and hence the magnetic properties. The CoFeMn0.5Alx alloys (0 < x <0.75) were fabricated using arc-melting, and characterised using X-ray diffraction (phases present), scanning electron microscope (composition) and SQUID magnetometry (magnetic properties as a function of magnetic field and temperature). It was found that for Al content of x < 0.2, there existed mixed FCC and BCC phases, while with further addition of Al, the BCC phase was stabilised (Figure 1a.). This lead to an increase in the saturation magnetisation and a decrease in the coercive field (Figure 1b). The alloy CoFeMn0.5Al0.25 was determined to have a competitive saturation magnetisation compared to CoFe, but with the reduction of Co concentration in the alloy should also be cheaper to produce.
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Figure 1a. XRD of the CoFeMn0.5Alx alloys. 1b Saturation magnetisation and coercive field as a function of Al concentration.