Magnetic Properties and Chemical Synthesis of FePt and CoPt Nanoclusters

ORAL

Abstract

Much interest has been paid to self-assembled L1$_{0}$ FePt and CoPt nanoclusters for basic science and potential applications in ultra-high density magnetic recording media. In this study, thermal decompostion of a Fe and Pt acetylacetonates mixture in trioctylamine was employed to produce FePt nanoclusters with average size about 4 nm and a narrow size distribution. The atomic ratio of Fe and Pt for the as-synthesized FePt clusters is 50:50. Using the same procedure, CoPt nanoclusters were obtained with the atomic ratio of 40:60. With the addition of oleic acid into the reaction solution the atomic ratios were adjusted to 50:50. As-synthesized FePt and CoPt nanoclusters have fcc structures, but after rapid thermal annealing in forming gas the nanoclusters transform into hard magnetic L1$_{0}$ ordered structures. The nanostructures of the clusters were characterized by TEM and XRD. The magnetic properties were measured by a SQUID magnetometer. The coercivity of FePt and CoPt clusters reached the maximum value of 23 kOe and 17kOe respectively after annealing at 750 $^{o}$C for 5mins. Beyond 750 $^{o}$C, the coercivity decreased slightly because of the sintering effect and a different magnetic reversal mechanism. This work is supported by NSF-MRSEC, DOE, INSIC, NRI and NCMN.

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Authors

  • Yao Zhao

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0111, USA, Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, NE, 68588-0113

  • Yucheng Sui

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0111, USA, Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, NE, 68588-0113, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0111, Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 USA

  • D.J. Sellmyer

    Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0111, USA, Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, NE, 68588-0113, Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, USA