One-step fabrication of L1 ₀ FePt nanocubes and rods by cluster beam deposition

In this work, single crystal L1 ₀ FePt nanocubes have been successfully produced by a cluster beam deposition technique without the need of post annealing. Particles have been deposited by dc magnetron sputtering using high Ar pressures on both single crystal Si substrates and Au grids for the measurement of magnetic and structural properties, respectively. The nanocubes have a uniform size distribution with an average size of 5 nm. At 1 Torr, the particles have the L1 ₀ structure with an order parameter of ₀.5 and a RT _coercivity of 2 kOe with high switching fields observed in the hysteresis loop. Further annealing increased the particle size to 20 nm and the RT _coercivity to 10.2 kOe with perfect chemical ordering. In addition to these nanocubes, micron size rods with the L1 ₀ structure have been observed near the cluster gun. SEM analysis showed that these rods consist of nanoparticles with 20 nm average size. Surfactant assisted high-energy ball milling has been used to separate the nanoparticles from the rods. After one hour of milling, these 20 nm particles showed a room temperature coercivity of 9 kOe with an order parameter of ₀.85. These FePt nanocubes have a potential for use in the development of future high-density magnetic recording media because of their high coercivity, good shape and very narrow size distribution.