Preparation of FePt Magnetic Nanoparticle Film by Plasma Chemical Vapor Deposition for Ultrahigh Density Data Storage Media

摘要

We prepared an FePt nanoparticle film for magnetic storage media using 13.56 MHz glow-discharge plasma. Vapors of metal organics, namely biscyclopentadienyl iron (ferrocene) for Fe and (methylcyclopentadienyl)trimethyl platinum for Pt, were introduced into a capacitively coupled flow—through plasma chamber, which consisted of a shower head RF electrode and a grounded orifice plate electrode. Synthesized nanoparticles were directly collected onto a transmission electron microscope (TEM) grid or MgO substrate placed just below the grounded orifice electrode. TEM images showed two kinds of particles, one of which was nanometer sized and isolated and the other appeared as a coagulate of small particles. The diameter of the coagulated particle was larger than 10nm. Nanometer size particles were separated and deposited on MgO substrate by adjusting the gas flow rate through the grounded orifice plate. The magnetization of the FePt nanoparticle film was evaluated by magneto-optical Kerr effect (MOKE) spectroscopy. As-synthesized nanoparticles did not exhibit a loop-shape magnetization curve. Annealing in atmospheric hydrogen was conducted to transform crystal from fcc structure to fct L10 ordered structure. The higher annealing temperature resulted in the more ordered L10 phase formation and the larger coercivity. A sample annealed at 750℃ exhibited a room temperature coercivity of 10 kOe. Also, it was confirmed that nanoparticle film density is critical to the magnetization.