A1 to L1(0) Transformation in FePt Films With Ternary Alloying Additions of Ag and Au

The formation of the ordered L1(0) phase from the parent A1 (face centered cubic, fcc) solid solution phase in ternary FeAgPt (1.5 - 16.7 at.% Ag) and FeAuPt (1.9 - 13.8 at.% Au) films has been studied. The films were co-sputter deposited from elemental targets at room temperature and annealed after deposition. The annealed films showed the presence of fcc Ag peaks for concentrations of 6.9 at.% Ag and higher and fcc Au diffraction peaks for concentration of 7.2 at.% Au and higher. Therefore, these two elements are not fully soluble in L1(0) FePt. The kinetic ordering temperature is higher in both types of ternary films when compared with binary FePt. However, the activation energy for ordering is higher only for high concentrations of Au. The enthalpy for decomposition of FeAgPt and FeAuPt into L1(0) FePt and Ag or Au is not measurably different than that for transformation of the A1 phase to the L1(0) phase in binary FePt. Ternary additions of Ag and Au have no impact on the Curie temperature of the L1(0) phase.