Magnetization dynamics of interacting iron nanocrystals inSiO2

Abstract

We find that ensembles of iron nanocrystals embedded within a matrix of SiO 2 exhibit both a large Faraday rotation and ultrafast magnetic relaxation. The Verdet constant is 6.3°± 0.4°/ cm/ Oe and a still-unsaturated Faraday rotation of 3.8°± 0.2°/ m was observed at a wavelength of 532 nm for a specimen containing nanocrystals ranging up to 20 nm in diameter. The dynamic response of the nanocrystals to a transient magnetic field produced by a current pulse propagating through a lithographically patterned wire was probed using time-resolved magneto-optical Kerr-effect microscopy. The rise time of the magnetic response to a transient out-of-plane field was observed to be as fast as 26 ps. Magnetostatic interactions between nanoparticles play a significant role in determining the observed static and dynamic properties of the nanocomposite.

Engineering embedded metal nanoparticles with ion beam technology

“…Moreover, both satellite NP sizes and their distance to the large NP surface have a linear increase with the nuclear energy loss of the irradiating ions. The formation of hollow nanoparticles were also observed in Fe [29] and Ag/Cd [30], Co/Ni (Cu/Ni) [31], Al/Fe (Fe/Al) [32], Pd/Ag (Pd/Fe) [33], and Fe/Pt [34] sequentially implanted samples with ion energies around 100 keV.…”

Broadband Ferromagnetic Resonance Measurements in Ni/ZnO and Niγ-Fe2O3Nanocomposites

“…As recalled earlier, an additional problem is particle oxidation arising from the large surface-area-to-volume ratio. The fundamental nature of oxidation in nanometersized structures has received some recent attention [60][61][62][63][64], however it is far from being well understood.…”

Multilayer route to iron nanoparticle formation in an insulating matrix

“…[9][10][11][12][13][14][15] The particle size strongly depends on the preparation parameters and methods and can be difficult to control. Ion implantation was shown to produce metallic iron nanoparticles that exhibited large Faraday rotation and fast dynamic response, 5,13,16 but the size distribution was wide. Effective size control has been pursued using self-assembly in ordered nanomaterials, [17][18][19] as well as chemical synthesis of monodispersed ferro/ferrimagnetic nanoparticles by reduction of metal salts and/or thermal decomposition of organometallic precursors.…”

“…15,[20][21][22][23] Size control down to the nanometer level has been well accomplished in the chemical synthesis or the combination of self-assembly and patterning techniques, but the unprotected metallic nanoparticles are susceptible to oxidation. [16][17][18][19] Development of useful nanocomposite materials and fabrication processes still poses a challenging problem. For a nanocomposite system, microstructural analysis is critical for understanding the physical properties, particularly because surface atoms in the metallic nanoparticles tend to be oxidized or bonded to the matrix.…”