Direct synthesis of oriented high-density Islands of L1₀-FePtCu alloy at 613 K

A low-temperature synthesis of isolated and oriented L1₀-FePtCu nanoparticles with high-density dispersion has been achieved by a conventional rf magnetron sputtering technique with a single crystal NaCl substrate. Hard magnetic L1₀-type ordered phase with a coercivity of about 1.4 kOe is directly formed at substrate temperatures as low as 613 K without any post-deposition annealing. With a decrease in sputtering duration, particle size and interparticle distance decrease. These nanoparticles have 〈100〉 orientation on the NaCl substrate. The alloy compositional change from particle to particle is quite small. Although the atomic ordering is confirmed even at 563 K, the intensity of the superlattice reflections is very weak. The thermal fluctuation of magnetization becomes prominent in specimens with particle size smaller than about 10nm in diameter.