scholarly journals Deconvolution of Ferromagnetic Resonance Spectrum of Magnetic Nanoparticle Assembly Using Genetic Algorithm

2021 ◽  
Author(s):  
N. A. Usov ◽  
O. N. Serebryakova
Keyword(s):  
Genetic Algorithm ◽  
Magnetic Anisotropy ◽  
Ferromagnetic Resonance ◽  
Magnetite Nanoparticles ◽  
Magnetic Moments ◽  
Spherical Shape ◽  
Thermal Fluctuations ◽  
Nanoparticle Assembly ◽  
Aspect Ratios ◽  
Exciting Frequency

Abstract The ferromagnetic resonance (FMR) spectra of dilute random assemblies of magnetite nanoparticles with cubic magnetic anisotropy and various aspect ratios are calculated using the stochastic Landau-Lifshitz equation at a finite temperature, T = 300 K, taking into account the thermal fluctuations of the particle magnetic moments. Particles of non-spherical shape in the first approximation are described as elongated spheroids with a given semiaxes ratio a/b, where a and b are the long and transverse semiaxes of a spheroid, respectively. A representative database of FMR spectra is created for assemblies of randomly oriented spheroidal magnetite nanoparticles with various transverse diameters D = 5 - 25 nm, moderate aspect ratios a/b = 1.0 - 1.8, and magnetic damping constants k = 0.1, 0.2. The basic FMR spectra of assemblies with D = 25 nm at different aspect ratios can be considered as representatives of assemblies of single-domain magnetite nanoparticles with transverse diameters D > 25 nm. The database is calculated at exciting frequency f = 4.9 GHz (S-band) to clarify clearly the details of the FMR spectrum that depend on the nature of the particle magnetic anisotropy. The data obtained make it possible to analyze arbitrary combined FMR spectra constructed as weighted linear combinations of FMR spectra of the base assemblies. In addition, using a genetic algorithm, the corresponding inverse problem is solved. The latter consists in determining the volume fractions of the base assemblies in some arbitrary nanoparticle assembly, which is represented by its FMR spectrum.PACS: 75.20.-g; 75.50.Tt; 75.40.Mg

scholarly journals Heating ability of magnetic nanoparticles with cubic and combined anisotropy

2019 ◽  
Vol 10 ◽  
pp. 305-314 ◽  
Author(s):  
Nikolai A Usov ◽  
Mikhail S Nesmeyanov ◽  
Elizaveta M Gubanova ◽  
Natalia B Epshtein
Keyword(s):  
Magnetite Nanoparticles ◽  
Magnetic Nanoparticle ◽  
Specific Absorption Rate ◽  
Magnetic Moments ◽  
Low Frequency ◽  
Hysteresis Loops ◽  
Dipole Interaction ◽  
Thermal Fluctuations ◽  
Fractal Clusters ◽  
Cubic Anisotropy

The low frequency hysteresis loops and specific absorption rate (SAR) of assemblies of magnetite nanoparticles with cubic anisotropy are calculated in the diameter range of D = 20–60 nm taking into account both thermal fluctuations of the particle magnetic moments and strong magneto–dipole interaction in assemblies of fractal-like clusters of nanoparticles. Similar calculations are also performed for assemblies of slightly elongated magnetite nanoparticles having combined magnetic anisotropy. A substantial dependence of the SAR on the nanoparticle diameter is obtained for all cases investigated. Due to the influence of the magneto–dipole interaction, the SAR of fractal clusters of nanoparticles decreases considerably in comparison with that for weakly interacting nanoparticles. However, the ability of magnetic nanoparticle assemblies to generate heat can be improved if the nanoparticles are covered by nonmagnetic shells of appreciable thickness.

Magnetic anisotropy in nanoscaled materials probed by ferromagnetic resonance

2006 ◽  
Vol 79 (9-10) ◽  
pp. 793-813 ◽  
Author(s):  
KH. Zakeri ◽  
TH. Kebe ◽  
J. Lindner ◽  
C. Antoniak ◽  
M. Farle ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Ferromagnetic Resonance

scholarly journals Effect of malaria parasite shape on its alignment at erythrocyte membrane

2021 ◽  
Author(s):  
Anil K Dasanna ◽  
Sebastian Hillringhaus ◽  
Gerhard Gompper ◽  
Dmitry A Fedosov
Keyword(s):  
Spherical Shape ◽  
Coarse Grained ◽  
Local Curvature ◽  
Stochastic Nature ◽  
Rbc Membrane ◽  
Aspect Ratios ◽  
Strong Adhesion ◽  
Alignment Process ◽  
Pointed End ◽  
Membrane Deformations

During the blood stage of malaria pathogenesis, parasites invade healthy red blood cells (RBC) to multiply inside the host and evade the immune response. When attached to RBC, the parasite first has to align its apex with the membrane for a successful invasion. Since the parasite's apex sits at the pointed end of an oval (egg-like) shape with a large local curvature, apical alignment is in general an energetically un-favorable process. Previously, using coarse-grained mesoscopic simulations, we have shown that optimal alignment time is achieved due to RBC membrane deformation and the stochastic nature of bond-based interactions between the parasite and RBC membrane (Hillringhaus et al., 2020). Here, we demonstrate that the parasite's shape has a prominent effect on the alignment process. The alignment times of spherical parasites for intermediate and large bond off-rates (or weak membrane-parasite interactions) are found to be close to those of an egg-like shape. However, for small bond off-rates (or strong adhesion and large membrane deformations), the alignment time for a spherical shape increases drastically. Parasite shapes with large aspect ratios such as oblate and long prolate ellipsoids are found to exhibit very long alignment times in comparison to the egg-like shape. At a stiffened RBC, spherical parasite aligns faster than any other investigated shapes. This study shows that the original egg-like shape performs not worse for parasite alignment than other considered shapes, but is more robust with respect to different adhesion interactions and RBC membrane rigidities.

scholarly journals Measurement of effective magnetic anisotropy field and ferromagnetic resonance bandwidth at ferromagnetic resonance frequency in magnetically uniaxial hexagonal ferrites

2019 ◽  
Vol 5 (1) ◽  
pp. 33-39
Author(s):  
Alexey S. Semenov ◽  
Aleksey G. Nalogin ◽  
Sergey V. Shcherbakov ◽  
Alexander V. Myasnikov ◽  
Igor M. Isaev ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Ferromagnetic Resonance ◽  
Transmission Lines ◽  
Anisotropy Field ◽  
Nominal Composition ◽  
Hexagonal Ferrites ◽  
Magnetic Texture ◽  
Measurement Results ◽  
Effective Magnetic Anisotropy ◽  
Ferromagnetic Resonance Frequency

In this work we have considered metrological problems and measurement of magnetic parameters and presented methods of measuring effective magnetic anisotropy field HAeff and ferromagnetic resonance bandwidth ∆H in magnetically uniaxial hexagonal ferrites in the electromagnetic microwave working frequency range. The methods allow measuring HAeff in the 10–23 and 28–40 kE ranges and ∆H in the 0.5–5.0 range. One method (suitable for wavelength measurements in free space in the 3-mm wavelength range) has been implemented for the 78.33–118.1 GHz range. The other method (based on the use of microstrip transmission lines) has been implemented for the 25–67 GHz range. The methods have been tested for polycrystalline specimens of hexagonal barium and strontium ferrites with nominal composition or complex substituted and having high magnetic texture. The measurement results have been compared with those obtained using conventional measurement methods and spherical specimens. Our methods prove to be highly accurate and reliable.

Large E-field tunability of magnetic anisotropy and ferromagnetic resonance frequency of co-sputtered Fe50Co50-B film

2015 ◽  
Vol 117 (17) ◽  
pp. 17D702 ◽  
Author(s):  
Shandong Li ◽  
Qian Xue ◽  
Honglei Du ◽  
Jie Xu ◽  
Qiang Li ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Resonance Frequency ◽  
Ferromagnetic Resonance ◽  
Ferromagnetic Resonance Frequency
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