Synthesis, structural characterization and magnetic properties of Fe/Pt core-shell nanoparticles

摘要: Structural and magnetic properties of Fe/Pt core-shell nanostructure prepared by a sequential reduction process are reported. Transmission electron microscopy shows nearly spherical particles fitting lognormal size distribution with Do = 3.0 nm width λD = 0.31. In x-ray diffraction, Bragg lines only from the Pt shell clearly identified line-widths yielding crystallite size = 3.1 nm. Measurements magnetization M vs. T (2 K–350 K) in fields up to 90 kOe show blocking temperature TB = 13 K below which hysteresis loops observed coercivity HC increasing decreasing reaching HC = 750 Oe at 2 K. Temperature dependence ac susceptibilities frequencies fm = 10 Hz–5 kHz is measured determine change TB fm using Vogel-Fulcher law. This analysis presence significant interparticle interaction, Neel-Brown relaxation frequency fo = 5.3 × 1010 Hz anisotropy constant Ka = 3.6 × 106 ergs/cm3. A fit H data u...