A facile synthesis of directly gas-phase ordered high anisotropic Sm Co based non-segregated nanoalloys by cluster beam deposition method

Synthesis of nanoalloys containing three or more elements with controllable size and morphology and desired phase is very challenging. Rare earth (RE)-transition metal (TM) nanoalloys have great potential applications, however, their controllable synthesis is even a daunting task. Here we find that the direct gas-phase ordering of Sm-Co-based nanoalloys (around 5–15 nm) into 1:5 phase without size and shape change can be achieved by in-flight annealing through reducing their crystallization-ordering temperature (COT) with additive Cu or Ni. The homogenous element-distribution and desired phase in these trimetallic nanoalloys are evidenced by high-resolution-transmission-electron-microscopy analysis despite a preferred surface segregation from thermodynamic calculation and analysis. Our results demonstrate a promising way to synthesize trimetallic nanoalloys especially RE-TM with independently controlled size, composition and phase as well as their building-blocks with novel functionalities. The reduction in COT of Sm-Co-Cu nanoalloys is further confirmed by post-annealing the deposited nanocluster film. A significant coercivity-enhancement is achieved at a lower annealing-temperature. Compared to FePt, the higher anisotropy and much lower COT of Sm-Co-based nanoalloy make it emerge as a promising next-generation recording media with density beyond FePt. Our study also opens a door for fabricating trimetallic or even multicomponent nanoalloys with controllable size, composition and phase. Keywords: Nanoalloys, Gas phase ordering, Crystallization temperature, Cluster beam deposition, High magnetic anisotropy