Direct Detection of Static Dipolar Interaction on a Single Nanodisk Using Microfocused Brillouin Light Scattering Spectroscopy

Shimon, G.; Adeyeye, A. O.

doi:10.1002/aelm.201500070

Cited by 6 publications

(3 citation statements)

References 45 publications

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“…[11][12][13][14][15][16] In fact, interactions are the basis of a large number of nanoparticle-based magnetic materials, e.g., superferromagnets, superspin glasses, artificial spin ice, long range self-assemblies, or ferrofluids. 15,[17][18][19][20][21] Given the crucial importance of interactions in magnetic nanostructures, many direct and indirect approaches have been used to try to quantify them: first order reversal curve (FORC) analysis, 22,23 small angle neutron scattering, SANS, [24][25][26][27] electron holography, 28,29 magnetic force microscopy, 30,31 Lorentz microscopy, 32 Brillouin light scattering, 33 resonant magnetic x-ray scattering 34 and so on. However, one of the most accepted methods to assess interactions is the remanence plots technique (i.e., Henkel or δM plots), [35][36][37] which is routinely used to evaluate interactions between nanoparticles or grains [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]…”

Section: Introductionmentioning

confidence: 99%

“…Exchange and dipolar interactions between grains or particles are essential to understanding the behavior of magnetic polycrystalline and colloidal materials. , Indeed, these interactions are key to the performance of many common magnetic materials, e.g., permanent magnets, , magnetic recording media, , and magnetically soft materials for high frequency applications, where dipolar interactions may have undesirable effects, such as aggregation of nanoparticles in biomedical applications. − Magnetic interactions control the properties of sufficiently dense assemblies of magnetic nanoparticles and nanostructures, tailoring their functional properties, e.g., blocking (or freezing) temperature, coercivity, remanent magnetization, switching-field distribution, and effective anisotropy, among others. − In fact, interactions are the basis of a large number of nanoparticle-based magnetic materials, e.g., superferromagnets, superspin glasses, artificial spin ice, long-range self-assemblies, or ferrofluids. ,− Given the crucial importance of interactions in magnetic nanostructures, many direct and indirect approaches have been used to try to quantify them: first-order reversal curve (FORC) analysis, , small angle neutron scattering, SANS, − electron holography, , magnetic force microscopy, , Lorentz microscopy, Brillouin light scattering, resonant magnetic X-ray scattering, and so on. However, one of the most accepted methods to assess interactions is the remanence plots technique (i.e., Henkel or δM plots), − which is routinely used to evaluate interactions between nanoparticles or grains − both in fundamental studies , and in diverse nanopar...…”

Section: Introductionmentioning

confidence: 99%

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Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

et al. 2017

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Remanence magnetization plots (e.g., Henkel or δM plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains.Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here we demonstrate that δM plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the δM plots of γ-Fe 2 O 3 nanoparticles isolated by thick SiO 2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. Our results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mössbauer measurements, that has a pronounced effect on the δM plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the δM plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions, as well as offer new perspectives in the use of Henkel-and δM-plots to quantify the rather elusive inhomogeneous magnetizations states in nanoparticles.Additional information on the δM and the in-field Mössbauer techniques, table with the complete results of the Mössbauer spectra fits, details of the Monte Carlo simulations, FC and ZFC magnetization curves of the VST series (Fig. S1a), Langevin scaling of M(H;T) data measured in VST45 (Fig. S1b), details on the estimate of the "magnetic size" from Langevin fits, δM plots of all the VST series and graphical analysis of the intraparticle and interparticle contributions to the dip (Fig. S2), example of hysteresis loops measured after ZFC and FC (for sample VST17, Fig. S3); X-ray diffraction patterns and lattice parameter across of the maghemite cores of different size (Fig. S4); complete results from Monte Carlo simulations showing the dependence of δM on core anisotropy (Fig. S5), surface anisotropy ( Fig. S6), exchange coupling constant ( Fig. S7) and disordered surface thickness (Fig. S8).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

et al. 2017

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“…The inter-dot distance is fixed at 2-μm for all arrays. For such a large edge-to-edge distance, the dipolar interaction between the neighboring elements is negligible and thus can be ignored 20 .…”

Section: Methodsmentioning

confidence: 99%

Spin Vortex Resonance in Non-planar Ferromagnetic Dots

Ding

Lapa

Jain

et al. 2016

Sci Rep

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In planar structures, the vortex resonance frequency changes little as a function of an in-plane magnetic field as long as the vortex state persists. Altering the topography of the element leads to a vastly different dynamic response that arises due to the local vortex core confinement effect. In this work, we studied the magnetic excitations in non-planar ferromagnetic dots using a broadband microwave spectroscopy technique. Two distinct regimes of vortex gyration were detected depending on the vortex core position. The experimental results are in qualitative agreement with micromagnetic simulations.

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Size-dependent magnetization dynamics in individual Ni80Fe20 disk using micro-focused Brillouin Light Scattering spectroscopy

Shimon

Adeyeye

2015

AIP Advances

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A direct and systematic investigation of the magnetization dynamics in individual circular Ni80Fe20 disk of diameter (D) in the range from 300 nm to 1 μm measured using micro-focused Brillouin Light Scattering (μ-BLS) spectroscopy is presented. At high field, when the disks are in a single domain state, the resonance frequency of the uniform center mode is observed to reduce with reducing disk’s diameter. For D = 300 nm, additional edge and end-domains resonant modes are observed due to size effects. At low field, when the disks are in a vortex state, a systematic increase of resonant frequency of magnetostatic modes in a vortex state with the square root of the disks’ aspect ratio (thickness divided by radius) is observed. Such dependence diminishes for disks with larger aspect ratio due to an increasing exchange energy contribution. Micromagnetic simulations are in excellent agreement with the experiments.

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Direct Detection of Static Dipolar Interaction on a Single Nanodisk Using Microfocused Brillouin Light Scattering Spectroscopy

Cited by 6 publications

References 45 publications

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

Spin Vortex Resonance in Non-planar Ferromagnetic Dots

Size-dependent magnetization dynamics in individual Ni80Fe20 disk using micro-focused Brillouin Light Scattering spectroscopy

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