New gold permanent magnet alloys

A gold permanent magnet for an ornamental material is developed in a Au-Fe-Co system. The magnetic properties of the various Au-based alloys are studied. It is found that the magnetic properties of the Au-7.2wt %Fe-4.8wt %Co alloy aged at 600°C for 10 min and subsequently controlled-cooled to 400°C at a cooling rate of 50°C/h, are Br = 0.27 T (2700 G), iHc = 41.2 kA/m (515 Oe), and (B-H) max = 3.4 kJ/m³(0.43 MGOe). The cold-swaging improved the magnetic properties of the alloy as Br = 0.34 T (3400 G), iHc = 81.2 kA/m (1015 Oe), and (B-H) max = 8.2 kJ/m³(1.03 MGOe). Microstructural observations indicate that the magnetic hardening is due to the fine iron-cobalt particles precipitated in the Au matrix.