Angular dependent ferromagnetic resonance analysis in a single micron sized cobalt stripe (original) (raw)
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Ferromagnetic Resonance Studies in Magnetic Nanosystems
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Ferromagnetic resonance is a powerful method for the study of all classes of magnetic materials. The experimental technique has been used for many decades and is based on the excitation of a magnetic spin system via a microwave (or rf) field. While earlier methods were based on the use of a microwave spectrometer, more recent developments have seen the widespread use of the vector network analyzer (VNA), which provides a more versatile measurement system at almost comparable sensitivity. While the former is based on a fixed frequency of excitation, the VNA enables frequency-dependent measurements, allowing more in-depth analysis. We have applied this technique to the study of nanostructured thin films or nanodots and coupled magnetic layer systems comprised of exchange-coupled ferromagnetic layers with in-plane and perpendicular magnetic anisotropies. In the first system, we have investigated the magnetization dynamics in Co/Ag bilayers and nanodots. In the second system, we have st...
Visualization of spin dynamics in single nanosized magnetic elements
Nanotechnology, 2011
The design of future spintronic devices requires a quantitative understanding of the microscopic linear and nonlinear spin relaxation processes governing the magnetization reversal in nanometer-scale ferromagnetic systems. Ferromagnetic resonance is the method of choice for a quantitative analysis of relaxation rates, magnetic anisotropy and susceptibility in a single experiment. The approach offers the possibility of coherent control and manipulation of nanoscaled structures by microwave irradiation. Here, we analyze the different excitation modes in a single nanometer-sized ferromagnetic stripe. Measurements are performed using a microresonator setup which offers a sensitivity to quantitatively analyze the dynamic and static magnetic properties of single nanomagnets with volumes of (100 nm) 3. Uniform as well as non-uniform volume modes of the spin wave excitation spectrum are identified and found to be in excellent agreement with the results of micromagnetic simulations which allow the visualization of the spatial distribution of these modes in the nanostructures.
Magnetic anisotropy in nanoscaled materials probed by ferromagnetic resonance
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Ferromagnetic resonance measurements probe the dynamical response of magnetic systems due to an excitation within the microwave regime. Offering high sensitivity and energy resolution in the meV range of ferromagnetic resonance this technique is well suited for the investigation of magnetic anisotropy in nanoscale systems. Ferromagnetic Resonance experiments give direct and quantitative access to magnetic anisotropy based on an analysis that uses the Landau-Lifshitz equation of motion. This will be demonstrated for the case of ultrathin magnetic 5-20ML thick Fe films on {4 Â 6}GaAs(001) (2D system) which have been grown and measured in situ in ultra high vacuum, magnetic MnAs stripes (1D system) grown on GaAs(001) as well as for arrays of highly monodisperse FePt nanoparticles (quasi 0D system).
Ferromagnetic Resonance in Nanometric Magnetic Systems
Encyclopedia of Materials: Science and Technology, 2008
Nanometric magnetic systems are of growing importance, displaying novel magnetic properties which are of both fundamental scientific interest as well as of practical importance. There are several types of system which can be classified as nanometric, which depend on the fabrication process, for example, amorphous / nanocrystalline alloys, immiscible alloys (e. g. Co -Cu), nanostructured films and discontinuous multilayer systems. In whatever case, magnetic confinement effects and the interactions between magnetic particles, via an intervening phase, give rise to the particular magnetic behaviour and properties of the system in question. Ferromagnetic resonance (FMR) is a powerful technique for the study of magnetic properties and has been applied to many different types of magnetic system. FMR essentially measures the internal effective field to which a spin system is subject and as such can reveal useful information on fundamental magnetic properties such as the g -factor, magnetisation, magnetocrystalline anisotropies and shape effects. In the present paper we present experimental results of FMR studies of FeZrCuB amorphous/nanocrystalline alloy, FeAl cluster systems and the discontinuous multilayer system Al 2 O 3 [CoFe(t)/Al 2 O 3 ] 10 , where t is the effective thickness, ranging from 7 to 13 Å.
This work provides a detailed investigation of the measured in-plane field-swept homodyne-detected ferromagnetic resonance (FMR) spectra of an extended Co/Cu/NiFe pseudo-spin-valve stack using a nanocontact (NC) geometry. The magnetodynamics are generated by a pulse-modulated microwave current, and the resulting rectified dc mixing voltage, which appears across the NC at resonance, is detected using a lock-in amplifier. Most notably, we find that the measured spectra of the NiFe layer are composite in nature and highly asymmetric, consistent with the broadband excitation of multiple modes. Additionally, the data must be fit with two Lorentzian functions in order to extract a reasonable value for the Gilbert damping of the NiFe. Aided by micromagnetic simulations, we conclude that (i) for in-plane fields the rf Oersted field in the vicinity of the NC plays the dominant role in generating the observed spectra, (ii) in addition to the FMR mode, exchange-dominated spin waves are also generated, and (iii) the NC diameter sets the mean wave vector of the exchange-dominated spin wave, in good agreement with the dispersion relation.
Note: Detection of a single cobalt microparticle with a microfabricated atomic magnetometer
Review of Scientific Instruments, 2011
We present magnetic detection of a single, 2 µm diameter cobalt microparticle using an atomic magnetometer based on a microfabricated vapor cell. These results represent an improvement by a factor of 10 5 in terms of the detected magnetic moment over previous work using atomic magnetometers to detect magnetic microparticles. The improved sensitivity is due largely to the use of small vapor cells. In an optimized setup, we predict detection limits of 0.17 µm 3 .