Dynamic Magnetic Hysteresis Research Articles

Dynamic magnetic characteristics and hysteresis behaviors of a diluted graphene-like monolayer

Dynamic magnetic characteristics and hysteresis behaviors of a diluted graphene-like monolayer

Effect of Cooling Rate on Dynamic Magnetic Hysteresis Loop Behaviors of Magnetic Materials by Using as a Model Mixed Spin (1, 3/2) Ising System Under an Oscillating Magnetic Field

Effect of Cooling Rate on Dynamic Magnetic Hysteresis Loop Behaviors of Magnetic Materials by Using as a Model Mixed Spin (1, 3/2) Ising System Under an Oscillating Magnetic Field

An improved dynamic magnetic hysteresis model in soft magnetic composites

In this paper, an improved static Jiles-Atherton (J-A) hysteresis model is proposed to simulate the hysteresis properties of soft magnetic composites (SMC) by introducing an excitation factor to control the rotational component of magnetic domains in the effective magnetic field based on the internal demagnetization effect and magnetization mechanism. On the other hand, Since SMC is usually applied in the mid-frequency band, an improved dynamic hysteresis model is necessary to be proposed. The analytical expression for calculating the intraparticle eddy current loss is proposed based on the microstructural parameters of the SMC. And the microstructural parameters are determined by discrete element method DEM. For the intraparticle eddy current loss, the squared term of the mean particle size in the expression is further clarified. Eventually, this improved dynamic J-A hysteresis model was derived through the theory of magnetic field separation. The results show that SMC hysteresis loops with magnetic flux densities up to 1.5 T and frequencies up to 1 kHz can be evaluated by the proposed model.

Nonlinear response of magnetization obeying inertial dynamics to superimposed dc and ac fields and dynamic magnetic hysteresis

The nonlinear ac stationary responses of magnetization and the dynamic magnetic hysteresis of ferromagnetic particles with uniaxial anisotropy acted on by both external dc and ac magnetic fields are evaluated by employing the inertial Landau–Lifshitz–Gilbert equation. Analytical expressions are obtained for the components of the second- and third-order nonlinear susceptibility tensors using the perturbation method. The dynamic nonlinear susceptibility strongly depends on the dc field strength. The effect of inertia on the area and slope of the dynamic magnetic hysteresis loop is demonstrated. In addition to nutation resonance, the main nonlinear effects previously observed in the ferromagnetic resonance region (frequency doubling and appearance of weak subharmonic resonance peaks) are predicted in the nutation resonance frequency region.

Determining the parameters of the dynamic magnetic hysteresis loop of the structural materials by attachable primary transducers

Coercive force, which is one of the structure-sensitive characteristics of ferromagnetic materials, is most often used for magnetic analysis. This approach requires the use of powerful magnetization systems, which leads to an increase in the size of the attachable magnetic probe and, accordingly, to a decrease in the locality of control. The above-mentioned disadvantages can be eliminated by using the parameters of the dynamic magnetic hysteresis loop (MHL), which involves the use of variable magnetic fields. A device for studying the dynamic MHL during cyclic remagnetization for the tasks of testing ferromagnetic materials, namely structural analysis, is proposed. The device consists of a generator of sinusoidal signals, an amplifier, a cur¬rent sensor, an attachable magnetic probe, a two-channel analog-to-digital converter (ADC), and a computer. The attachable magnetic probe is proposed in the form of a U-shaped core with magnetization windings on one leg and measurement winding on the other leg. The signal from the generator through the amplifier and the current sensor enters the magnetization winding. The ADC receives two signals: first one – from the measurement winding, and second – from the current sensor. Both signals from the ADC output in digital form are processed and analyzed by the computer using the developed specialized software in the LabVIEW language. Due to the developed software the filtering and integration of the signal from the measuring winding as well as the MHL plotting and MHL parameters calculation was realized. To reduce interference when determining MHL parameters, averaging over 50 magnetization cycles was performed. The attachable magnetic probe with the dimensions of the contact part 30x17 mm created a field with a strength of 300 A/m at a frequency of 50 Hz. The device was tested on specimens of sheet steel of 09G2S type with a thickness of 4 mm, in which uniaxial tensile stresses were created. The obtained results show the sensitivity of the dynamic MHL area to mechanical tensile stresses, as it increases from 14.8 to 16.8 mT A/m during loading.

Dynamic magnetic hysteresis features of a mixed spin (2, 5/2) Ising system on a hexagonal lattice under an oscillating magnetic field within the path probability method

Recently, we [J. Magn. Magn. Mater. 514 (2020) 167242] presented a study of the dynamic magnetic loop features of molecular-based magnetic materials and ferrimagnetism that were investigated by using a mixed spin 1/2 and spin-1 ferrimagnetic Ising system within the path probability method. We found several interesting dynamic magnetic hysteresis properties and observed that the obtained results are in qualitatively good agreement with some theoretical and experimental studies in magnetic materials. We extended our recent previous published work to study the dynamic magnetic hysteresis properties of molecular-based magnetic materials and ferrimagnetism utilizing the mixed spin (2, 5/2) ferrimagnetic Ising system on a hexagonal lattice employing the path probability method. The spin (2, 5/2) Ising system is one of the most suitable and most used prototypical systems to investigate many molecular-based magnetic materials and ferrimagnetic materials. We found more interesting dynamic magnetic hysteresis properties such as double, triple, quadruple and quintuple loop behaviors for the layer magnetization, and only double and triple loops for the total magnetization. We found that some of our obtained results are in qualitatively good agreement with some theoretical, experimental reported works, and the works on some magnetic materials as obtained by the melt-spinning technique.

The Effect of Magnetization Reversal Frequency on the Dynamic Magnetic Hysteresis of a Plate Made of Electrical Stee

Electrodynamic, quasi-static magnetic hysteresis loops and the form of the domain texture of a single-crystal plate have been experimentally obtained. Using mathematical modeling, the change in the dynamic magnetic hysteresis (the magnetic loss energy per unit volume per magnetization reversal cycle) depending on the frequency of the magnetic field is shown. This dependence is due to the inertia of the magnetization of the sample. With a change in frequency, the dynamic magnetic hysteresis can differ significantly from the hysteresis in the case of quasi-static magnetization reversal.

The Effect of Magnetization Reversal Frequency on the Dynamic Magnetic Hysteresis of a Plate Made of Electrical Steel

The Effect of Magnetization Reversal Frequency on the Dynamic Magnetic Hysteresis of a Plate Made of Electrical Steel

Large refrigerant capacity in superparamagnetic iron nanoparticles embedded in a thin film matrix

A magnetocaloric effect (MCE) with sizable isothermal entropy change (ΔS) maintained over a broad range of temperatures above the blocking temperature is reported for a rare earth-free superparamagnetic nanoparticle system comprising of Fe–TiN heterostructure. Superparamagnetic iron (Fe) particles were embedded in a titanium nitride (TiN) thin film matrix in a TiN/Fe/TiN multilayered pattern using a pulsed laser deposition method. High angle annular dark-field images in conjunction with dispersive energy analysis, recorded using scanning transmission electron microscopy, show a clear presence of alternating layers of Fe and TiN with a distinct atomic number contrast between Fe particles and TiN. Quantitative information about the isothermal entropy change (ΔS) and the magnetocaloric effect in the multilayer Fe–TiN system has been obtained by applying Maxwell relation to the magnetization vs temperature data at various fields. With the absence of a dynamic magnetic hysteresis above the blocking temperature, the negative ΔS as high as 4.18 × 103 J/Km3 (normal or forward MCE) is obtained at 3 T at 300 K.

Dynamic Magnetic Hysteresis Modeling Based on Improved Parametric Magneto-Dynamic Model

For the difficulty of accurate simulation of dynamic hysteresis loop at high frequency, a simple and effective method is proposed. Firstly, combined with accuracy and generality, the classical inverse Jile-Atherton (J-A) model is selected to simulate the hysteresis characteristics. The parameters of the J-A model are identified by the velocity controlled particle swarm optimization (VCPSO); Secondly, combined with the characteristics of high-frequency magnetic field distribution of silicon steel, an improvement of the parametric magneto dynamics is proposed to accurately calculate the magnetic field corresponding to eddy current loss. Finally, according to the theory of Bertotti model, the magnetic field corresponding to excess loss is introduced to ensure the accuracy of total dynamic magnetic field strength simulation. The effectiveness of the method is verified by a comparison with the measured hysteresis cycle. In addition, under the coupling of improved parametric magneto dynamics (IPMD) model and J-A model, the high-frequency power loss can be accurately predicted.

A hybrid Jiles–Atherton and Preisach model of dynamic magnetic hysteresis based on backpropagation neural networks

Ferromagnetic materials are widely used for magnetic cores in electromagnetic devices such as inductors, transformers, generators, and motors. In a magnetic core, as the magnetic field varies with time, core loss is generated due to magnetic hysteresis and eddy currents. For performance analysis and design optimization of electromagnetic devices, it is essential to model the dynamic magnetization processes and associated core losses accurately. This paper proposes a hybrid model of dynamic magnetic hysteresis, which incorporates the effects of both hysteresis and eddy currents, by combining the dynamic Jiles-Atherton and Preisach models based on backpropagation neural networks. This model can accurately reproduce the dynamic hysteresis loops and core losses under different excitations. The numerical simulations are verified by experimental measurements.

Dynamic magnetic hysteresis loop features of a mixed spin (1/2, 1) Ising system on a hexagonal lattice using path probability method

Batı and Ertaş [Physica B 513 (2017) 40] presented a study of dynamic magnetic hysteresis loop properties (DMHLFs) of a mixed spin (1/2, 1) Ising system (IS) on a hexagonal lattice within the mean-field theory based on the Glauber dynamics approach. They observed a number of interesting DMHLFs. We extended the investigation of DMHLFs of a mixed spin (1/2, 1) IS on a hexagonal lattice using the path probability method. We also examined the influences of the rate constants on DMHLFs as well as magnetic coercive fields and remanent magnetizations. We observed that some of our results are in quantitatively good agreement with some theoretical works on various ISs and experimental reported works on some magnetic materials as well as works within the melt-spinning method. We also found that the effects of rate constants are more effective on DMHLFs of the magnetization of spin-1 particles than loops of the magnetization of spin-1/2 particles.

Impact of Sn4+ substitution in Mg–Zn ferrites: Deciphering the structural, morphological, dielectric, electrical and magnetic properties

From the viewpoint of enormous applications and research, ferrite materials have already been achieved the status of one of the important branches of materials science. In this report, we have tuned the physical properties of Mg–Zn ferrites by Sn substitution investigated using X-ray diffraction, field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FTIR) spectroscopy, electrical and dielectric properties and quantum design physical properties measurement system. The Mg0·5Zn0.5SnxFe2-xO4 (0 ≤ x ≤ 0.10) samples have been synthesized by the conventional ceramic technique. The studied ferrites exhibits the single-phase up to x = 0.08 where an increase in lattice constant was observed. The FESEM images revealed the microstructure and the energy dispersive spectroscopy (EDS) confirms the absence of any unwanted elements. The increase (decrease) in bulk density (porosity) was associated with the variation of average grain size. FTIR spectra confirmed the formation of spinel structure. The dielectric polarization or conduction mechanism in these materials is due to the hopping of charge carriers at the octahedral sites. The common dielectric behavior of studied compositions is also observed. The substitution of Sn ions leads to enhanced dielectric constant and ac conductivity due to increased hopping of charge carriers. Complex impedance spectroscopy study revealed the non-Debye type of relaxation process within the studied compositions with a dominant contribution from grain boundary resistance. The dynamic magnetic hysteresis loops are measured to obtain the magnetic parameters. The low values of coercivity revealed the soft magnetic nature of the studied compositions. The obtained saturation magnetization (Ms) for Mg–Zn ferrite (x = 0.00) is comparable with the prior result. Non-linear decrease of Ms (62-44 emu/g) due to Sn substitution is explained based on the variation of magnetic moments over A- and B-sites. The squareness ratio (Mr/Ms) revealed that the magneto-statical interaction is present within the synthesized samples. The constant value of initial permeability (μʹ) over a wide range of frequencies revealed the compositional stability and quality of the prepared ferrite. The variation of μʹ with Sn content is similar to that of Msvs Sn contents. Moreover, theoretical cation distribution and the effect of Sn substitution on the related parameters have also been studied. The studied parameters are compared with the reported results, where available.

Di- and tri-component spinel ferrite nanocubes: synthesis and their comparative characterization for theranostic applications.

Spinel ferrite nanocubes (NCs), consisting of pure iron oxide or mixed ferrites, are largely acknowledged for their outstanding performance in magnetic hyperthermia treatment (MHT) or magnetic resonance imaging (MRI) applications while their magnetic particle imaging (MPI) properties, particularly for this peculiar shape different from the conventional spherical nanoparticles (NPs), are relatively less investigated. In this work, we report on a non-hydrolytic synthesis approach to prepare mixed transition metal ferrite NCs. A series of NCs of mixed zinc-cobalt-ferrite were prepared and their magnetic theranostic properties were compared to those of cobalt ferrite or zinc ferrite NCs of similar sizes. For each of the nanomaterials, the synthesis parameters were adjusted to obtain NCs in the size range from 8 up to 15 nm. The chemical and structural nature of the different NCs was correlated to their magnetic properties. In particular, to evaluate magnetic losses, we compared the data obtained from calorimetric measurements to the data measured by dynamic magnetic hysteresis obtained under alternating magnetic field (AMF) excitation. Cobalt-ferrite and zinc-cobalt ferrite NCs showed high specific adsorption rate (SAR) values in aqueous solutions but their heating ability was drastically suppressed once in viscous media even for NCs as small as 12 nm. On the other hand, non-stoichiometric zinc-ferrite NCs showed significant but lower SAR values than the other ferrites, but these zinc-ferrite NCs preserved almost unaltered their heating trend in viscous environments. Also, the presence of zinc in the crystal lattice of zinc–cobalt ferrite NCs showed increased contrast enhancement for MRI with the highest T2 relaxation time and in the MPI signal with the best point spread function and signal-to-noise ratio in comparison to the analogue cobalt-ferrite NC. Among the different compositions investigated, non-stoichiometric zinc-ferrite NCs can be considered the most promising material as a multifunctional theranostic platform for MHT, MPI and MRI regardless of the media viscosity in which they will be applied, while ensuring the best biocompatibility with respect to the cobalt ferrite NCs.

Super-Antiferromagnetics Nanoparticles for Magnetic Hyperthermia Applications: Effect of the Dc and Ac Magnetic Field

The importance of magnetic hyperthermia cancer treatments is based on the magnetic characteristic of the nanoparticles and their dependence on the DC and AC magnetic fields. In this paper we Study the dynamic magnetic hysteresis (DMH) of Super Antiferromagnetic nanoparticle, we use Brown’s continuous diffusion model to we evaluate the hysteresis loops, for extensive ranges of the anisotropy, the ac and dc magnetic fields.

General Regularities and Differences in the Behavior of the Dynamic Magnetization Switching of Ferrimagnetic (CoFe2O4) and Antiferromagnetic (NiO) Nanoparticles

In antiferromagnetic (AFM) nanoparticles, an additional ferromagnetic phase forms and leads to the appearance in AFM nanoparticles of a noncompensated magnetic moment and the magnetic properties typical of common FM nanoparticles. In this work, to reveal the regularities and differences of the dynamic magnetization switching in FM and AFM nanoparticles, the typical representatives of such materials are studied: CoFe2O4 and NiO nanoparticles with average sizes 6 and 8 nm, respectively. The high fields of the irreversible behavior of the magnetizations of these samples determine the necessity of using strong pulsed fields (amplitude to 130 kOe) to eliminate the effect of the partial hysteresis loop when studying the dynamic magnetic hysteresis. For both types of the samples, coercive force HC at the dynamic magnetization switching is markedly higher than HC at quasi-static conditions. HC increases as the pulse duration τP decreases and the maximum applied field H0 increases. The dependence of HC on field variation rate dH/dt = H0/2τP is a unambiguous function for CoFe2O4 nanoparticles, and it is precisely such a behavior is expected from a system of single-domain FM nanoparticles. At the same time, for AFM NiO nanoparticles, the coercive force is no longer an unambiguous function of dH/dt, and the value of applied field H0 influences more substantially. Such a difference in the behaviors of FM and AFM nanoparticles is caused by the interaction of the FM subsystem and the AFM “core” inside AFM nanoparticles. This circumstance should be taken into account when developing the theory of dynamic hysteresis of the AFM nanoparticles and also to take into account their practical application.

Features of the quasi-static and dynamic magnetization switching in NiO nanoparticles: Manifestation of the interaction between magnetic subsystems in antiferromagnetic nanoparticles

We report on the investigations of a system of 8-nm NiO particles representing antiferromagnetic (AFM) materials, which are weak magnetic in the form of submicron particles, but can be considered to be magnetoactive in the form of nanoparticles due to the formation of the uncompensated magnetic moment in them. The regularities of the behavior of magnetization switching in AFM nanoparticles are established by studying the magnetic hysteresis loops under standard quasi-static conditions and in a quasi-sinusoidal pulsed field of up to 130 kOe with pulse lengths of 4–16 ms. The magnetic hysteresis loops are characterized by the strong fields of the irreversible magnetization behavior, which is especially pronounced upon pulsed field-induced magnetization switching. Under the pulsed field-induced magnetization switching conditions, which are analogous to the dynamic magnetic hysteresis, the coercivity increases with an increase in the maximum applied field H0 and a decrease in the pulse length. This behavior is explained by considering the flipping of magnetic moments of particles in an external ac magnetic field; however, in contrast to the case of single-domain ferro- and ferrimagnetic particles, the external field variation rate dH/dt is not a universal parameter uniquely determining the coercivity. At the dynamic magnetization switching in AFM nanoparticles, the H0 value plays a much more important role. The results obtained are indicative of the complex dynamics of the interaction between magnetic subsystems formed in AFM nanoparticles.

Dynamic magnetic hysteresis loop features of molecular-based magnetic materials and ferrimagnetic systems by the path probability method

Dynamic magnetic hysteresis loops (DMHL) features of molecular-based magnetic materials and ferrimagnetic systems are investigated by a mixed spin (1/2, 1) model by means of the path probability method (PPM). The PPM contains two rate constants; hence the DMHL features have been studied by using the method with two rate constants. In particular, the effects of the repulsive (J<0) and attractive (J>0) bilinear nearest-neighbor pair interactions, temperature (T), crystal-field interaction (D), angular frequency (ω) of the oscillating magnetic field and especially the rate constant (k2), which corresponds to the wheel speed in the melt spinning technique (MST), on the DMHL are investigated. The shapes and areas of hysteresis loops are affective sensibility by these system parameters. We also investigate the magnetic coercive fields and remanents magnetizations as a function ω. We found that the most of our results are in a good agreement with some theoretical and experimental reported works. We also observe the novel and interesting DMHL behaviors for lower values of T, and higher values of ω, k2 and D.

Coarse-graining in micromagnetic simulations of dynamic hysteresis loops

We use micromagnetic simulations based on the stochastic Landau–Lifshitz–Gilbert equation to calculate dynamic magnetic hysteresis loops at finite temperature that are invariant with simulation cell size. As a test case, we simulate a magnetite nanorod, the building block of magnetic nanoparticles that have been employed in preclinical studies of hyperthermia. With the goal to effectively simulate loops for large iron-oxide-based systems at relatively slow sweep rates on the order of 1 Oe ns−1 or less, we modify and employ a previously derived renormalization group approach for coarse-graining (Grinstein and Koch 2003 Phys. Rev. Lett. 20 207201). The scaling algorithm is shown to produce nearly identical loops over several decades in the model cell volume. We also demonstrate sweep-rate scaling involving the Gilbert damping parameter that allows orders of magnitude speed-up of the loop calculations.

Stochastic magnetic resonance of absorption effects of surface morphology in thin film magnetics

The effect of surface roughness in thin film magnetics on magnetic susceptibility and Dynamic Magnetic Hysteresis (DMH) loops are investigated using Brown’s continuous diffusion of magnetic spins model. The magnetic relaxation time of the magnetic thin films is determined by regressing the two-mode approximation for the magnetic susceptibility onto experimental data obtained for Ni45Fe55. There is a moderate linear correlation between the magnetic relaxation time and the surface roughness to the thickness (SRT) ratio. The area of the DMH loops and the non-linear dynamic magnetic susceptibility strongly depend on the magnetic relaxation time and the SRT of the films. The thin films exhibit a strong linear relationship between the coercivity and the SRT ratio, along with a strong logarithmic dependence of the dynamic magnetic susceptibility on the SRT ratio.