An inductive technique for the measurement of dynamical magnetic processes in thin-film materials is described. The demonstrated using 50 nm films Permalloy (Ni81Fe19). Data are presented impulse- and step-response experiments with applied field pulse oriented plane film transverse to anisotropy axis. Rotation times as short 200 ps free oscillations magnetization after excitation clearly observed. oscillation frequency increases dc bias parallel axis predicted by classical gyromagnetic...

Abstract A method is developed to fabricate monodispersed biocompatible Yb/Er or Yb/Tm doped β‐NaGdF 4 upconversion phosphors using polyelectrolytes prevent irreversible particle aggregation during conversion of the precursor, Gd 2 O(CO 3 ) •H O:Yb/Er Yb/Tm, :Yb/Er Yb/Tm. The polyelectrolyte on outer surface nanophosphors also provided an amine tag for PEGylation. This employed PEGylated magnetic with Fe O as core and a shell. These have relatively high saturation magnetization (7.0 emu g −1...

We have measured the in-plane magnetization dynamics of Ni81Fe19 films using surface- and interface-sensitive second-harmonic magneto-optic Kerr effect. The dynamical was on patterned stripes as a function an magnetic field applied parallel to anisotropy axis. excitation sources were 100 ps risetime impulses steps. minimum switching times <300 ps, precessional free-induction decay observed. for both impulse step are fitted Landau–Lifshitz equation, yielding values field, gyroscopic...

We report a novel nanomanufacturing technique that incorporates patterned arrays built entirely from Fe3O4 nanoparticles into flexible and transparent polymer film. First, the are using enormous magnetic field gradients at surface of commercial disk drive media, then resulting architecture is transferred to film by spin-coating peeling. Since particles immobilized during process, array preserved after To demonstrate potential this technology, we fabricate 5 mm diameter all-nanoparticle...

We demonstrate a method of eliminating overshoot and ringing in magnetization dynamics when the system bandwidth includes intrinsic ferromagnetic resonance (FMR). The employs staggered step excitation for cancellation FMR oscillations while maximizing risetime response. second-harmonic magneto-optic Kerr effect is used to measure magnetic response at localized spot on sample. measured adequately modeled with Landau–Lifshitz–Gilbert differential equation. explain observed behavior terms...

We demonstrate reliable manipulation of the magnetization dynamics a precessing nanomagnet by precisely controlling spin transfer torque on subnanosecond time scale. Using simple pulse shaping scheme consisting two ultrafast pulses with variable amplitudes and delay, we coherent control over precessional orbits ability to tune switching probability at room temperature 77 K. Our measurements suggest that appropriately shaped can be used efficiently manipulate orientation free layer...

A two-dimensional, dynamic, micromagnetic model of a thin strip permalloy is described and used to the magnetization dynamics as it subjected transverse step field. The numerical results are compared experimental data. precession frequency matched by varying Hk, longitudinal, uniaxial, magnetocrystalline anisotropy damping α, phenomenological parameter in LLG equation. good fit data was obtained with single constant α=0.013.

User‐programmed meso‐ to microscale 2D shapes using magnetic nanoparticles as building blocks with magnetic‐field‐directed self‐assembly are created. The assembly templates magnetically recorded perpendicular recording (PMR) media. results demonstrate that PMR can template user‐designed features in two dimensions down 30 nm size, i.e., the nanoparticle diameter. It has been also shown assemble onto transitions between oppositely magnetized regions medium. At these transitions, field...

We have written and read back bits on perpendicular pre-patterned media prepared by electron-beam lithography. Using a contact tester equipped with standard longitudinal head, we are able to write different bit lengths 100×200 nm2 dots spaced 100 nm apart. These tests demonstrate the role played distribution of coercive fields during process. Signal-to-noise ratios (SNRs) obtained numerical analysis found be same order magnitude as in continuous media, but remain constant at decreasing...

Soft, high moment materials are crucial for the magnetic data recording industry in applications such as write poles and soft underlayers. Ever increasing areal densities have pushed requirements exhibiting saturation magnetizations above 2 T. In this work we investigate nanocrystalline FeCoB which exhibits a magnetization of ∼2.2 magnetostriction >50×10−6 suggests that magnetoelastic anisotropy is important. Nanocrystalline films rf diode sputtered function Ar pressure. As pressure...

Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufacturing. Understanding how these particles interact collectively fluids, especially they assemble aggregate under external fields, is critical high quality, safe, reliable deployment of particles. Here, by applying forces that vary strongly over the same length scale as colloidal stabilizing force then varying this repulsion, we can trigger self-assembly into parallel line patterns on surface a...

During the synthesis of nanoparticles via thermal decomposition iron precursors, capping ligand–precursor ratio influences resulting size oxide nanoparticles. As molar aliphatic amines to precursor is increased, average diameter synthesized decreases. This trend opposite previously reported results. We investigated this phenomenon by independently varying ligand chain length, ratio, and degree saturation chain. Nuclear magnetic resonance spectra illustrated presence a primary amine peak...

Using the enormous magnetic field gradients present near surface of recording media, we assemble diffraction gratings with lines consisting entirely self-assembled nanoparticles that are transferred to flexible polymer thin films. These nanomanufactured have line spacings programmed commercial and inherently concave radii curvature controlled by varying film thickness. This manufacturing approach offers a low-cost alternative for realizing more complex optical materials assembled...

We report second-harmonic magneto-optic Kerr measurements on air-exposed, polycrystalline Ni81Fe19 thin films, ranging in thickness from 1 nm to 2 μm, Al2O3 coated Si (001). For samples thicker than 20 nm, the transverse geometry, we observe a factor of 4 change intensity upon magnetization reversal. samples, interference between fields various interfaces and deterioration ferromagnetism films. Modeling suggests that Ni81Fe19/Al2O3 interface has larger second-order susceptibility...

We study magnetic-field directed self-assembly of magnetic nanoparticles onto templates recorded on perpendicular recording media, and quantify feature width height as a function assembly time. Feature widths are determined from Scanning Electron Microscope (SEM) images, while heights obtained with Atomic Force Microscopy (AFM). For short times, were ~150 nm, ~14 single nanoparticle average 10:1 aspect ratio. long approach 550 the grows to 3 nanoparticles, ~35 nm; 16:1 perform magnetometry...

A critical parameter in characterizing the properties of single-domain nanoparticles is their magnetic relaxation time. It must be known, for example, to estimate anisotropy from magnetization versus temperature measurements. The time it takes relax also determines behavior particles various oscillating applied fields, which critically important application particle imaging and hyperthermia treatment. However, an analytic expression this has been generally missing. Brown's [Phys. Rev. 130,...

Abstract 1D multiferroic fibers are known to exhibit attractive characteristics, including enhanced magnetoelectric (ME) coupling compared thin film and bulk architectures. A comprehensive understanding of composite fibers, however, has been hindered by the complexity their structure, leading limited reports. Here, clear strong ME is experimentally detected in a Janus nanofiber aggregate using second harmonic generation (SHG) polarimetry under different magnetic field orientations. The...

Measurements of magnetization response times in thin-film Permalloy are made by both electrical and optical methods. The method measures the inductive voltage generated a waveguide changing magnetization. technique uses standard pump-probe sampling methods combined with second-harmonic magneto-optic Kerr effect to directly measure angle as function time. Results these measurements for 75 nm thick film good qualitative agreement.

We demonstrate 27 ± 11 nm precision using stray magnetic fields from hard disk drive media to assemble 13 Fe3O4 nanoparticles in de-ionized water. By aligning the substrate polishing striations found atomic force microscopy (AFM) images of topography, we determine variance multiple nanoparticle coatings. The widths assembled features are ∼200 nm, and always distinct when separated by a median distance 500 nm. As these predictably follow field gradient, trapped offer nanoscale metrology for...