The phase equilibria, A2/B2 and B2/L21 order-disorder transitions and ferromagnetic/paramagnetic transition on the Co-Fe side of the Co-Fe-Ga system were examined by electron probe microanalysis (EPMA), differential scanning calorimetric (DSC) measurement and vibrating sample magnetometer (VSM). The equilibrium compositions of interrelations mainly among γ (A1: disordered fcc-Co), α (A2: disordered bcc-Fe), β (B2: ordered bcc-CoGa or FeGa) and β′ (L21 or D03: ordered bcc-Co2FeGa or Fe3Ga) phases were determined using diffusion couples and two-phase bulk specimens. It was confirmed that a bcc single-phase region composed of α, β and β′ at 700-1000° C exists in a wide composition range and that the ferromagnetic region appearing on the Co-Fe side extends to the center of the Gibbs triangle with decreasing temperature. On the other hand, the β′ phase appears along the Fe3Ga-Co3Ga section and the maximal critical temperature of the B2/L21 order-disorder transformation was determined to be 825 °C at a stoichiometric composition expressed as Co2FeGa. The obtained phase diagram was examined in comparison with that of the Co-Fe-Al system.
- Data storage materials
- Magnetic measurements