Effect of Ag addition to L1 FePt and L1 FePd films grown by molecular beam epitaxy

Abstract

L10 ordered FePt-Ag (5 nm) and FePd-Ag (5 nm) films were grown on MgO (001) substrate at temperatures of 250–400 °C by using molecular beam epitaxy method, and their crystal and surface structures, perpendicular magnetic anisotropies and Curie temperatures were investigated. In the case of FePt-Ag, Ag addition with the amount of 10–20 at. % was effective to promote L10 ordering and granular growth, resulting in the increase of the perpendicular magnetic anisotropy and coercivity of the FePt-Ag films. On the other hand, in the case of FePd-Ag, Ag addition changed the surface morphology from island to continuous film associated with the reductions of its coercivity and perpendicular anisotropy. The variations of lattice constants and Curie temperature with Ag addition were significantly different between FePt-Ag and FePd-Ag. For FePd-Ag, the c and a axes lattice spacings and Curie temperature gradually changed with increasing Ag content, while they unchanged for FePt-Ag. These results suggest the possibility of the formation of FePdAg alloy in FePd-Ag, while Ag segregation in FePt-Ag.

Structure and Magnetic Properties of (001) Oriented CoPt-Ag and CoPd-Ag Alloy Films

“…By comparing these results with those of the previously reported FePt-Ag and FePd-Ag 12) , we found a similarity between FePt-Ag and CoPt-Ag. For both alloys, Ag addition enhanced their PMA and coercivity as shown in Fig.…”

“…7 and Ref. 12), owing that the Ag addition promoted the L10 ordering and granular growth. Also, there exists a similarity between FePd-Ag and CoPd-Ag; Ag addition did not contribute to enhance the coercivity in both alloys.…”

“…We have also studied FePt-Ag and FePd-Ag films to investigate the effect of Ag addition into L10 phase magnetic materials 10)- 12) , and reported Ag addition to FePt with the amount of around 10 at. % is effective to promote L10 ordering and granular growth of FePt, resulting in the increase of the PMA and coercivity of the film normal direction.…”

“…% is effective to promote L10 ordering and granular growth of FePt, resulting in the increase of the PMA and coercivity of the film normal direction. From the structural analysis and magnetic properties measurements, it was concluded that the Ag is segregated from FePt, and this phase separation promotes L10 ordering and granular growth of FePt 12) . Unlike the case of FePt-Ag, Ag addition into FePd does not contribute to the corecivity increase and granular growth, and the formation of FePd-Ag alloy was observed 12) .…”

“…From the structural analysis and magnetic properties measurements, it was concluded that the Ag is segregated from FePt, and this phase separation promotes L10 ordering and granular growth of FePt 12) . Unlike the case of FePt-Ag, Ag addition into FePd does not contribute to the corecivity increase and granular growth, and the formation of FePd-Ag alloy was observed 12) . This suggests that the phase separation is a key factor to control the microstructure of L10 phase magnetic materials and to obtain suitable magnetic properties for the perpendicular recording media.…”