Single-domain Magnetic Particles Research Articles

Flow and Heat Transfer of Micropolar Ferrofluid at Stagnation Point on a Horizontal Flat Plate in the Presence of Magnetic Field and Thermal Radiation

Ferrofluid demonstrates Newtonian or non-Newtonian fluid behaviour depending on the characteristics of ferrofluid. Generally, ferrofluid consists of a stable colloidal suspension of single-domain magnetic particles in a base fluid that can assume non-Newtonian fluid behaviour involving a spin vector and microinertia tensor in flow motion. These two properties possess the theory of micropolar fluid which exhibits microrotational motions and spin inertia in microscopic behaviour. Therefore, this theoretical study is focused to investigate the boundary layer of micropolar ferrofluid flow and heat transfer at the stagnation point on the horizontal flat plate. Magnetite (Fe3O4) nanoparticles and water (H2O) compose in ferrofluid exposed to the magnetic field and thermal radiation is considered. The influences of ferroparticles volume fraction and micropolar parameter on the ferrofluid flow and heat transfer are evaluated mathematically. The partial differential equations have been formulated based on purposed assumptions using Tiwari and Das model and are simplified into ordinary differential equations, which are then solved numerically by Runge-Kutta Fehlberg (RFK45) method. The numerical results of the velocity profile, temperature profile, angular velocity profile, reduced skin friction and reduced Nusselt number are scrutinised in different values of ferroparticles volume fraction and micropolar parameter to estimate the ferrofluid flow and heat transfer. It is found the velocity profile of micropolar ferrofluid flow increases when elevates the ferroparticles volume fraction but decreases when increasing the micropolar parameter. Meanwhile, enlarging ferroparticles volume fraction of micropolar ferrofluid also enhances the temperature profile, reduced skin friction and reduced Nusselt number in the presence of magnetic field and thermal radiation parameter.

Effect of La3+/Cu2+ and La3/Ni2+ substitution on the synthesis, magnetic and dielectric properties of M−type Sr1-xLaxFe12-xMxO19 (M = Cu and Ni) hexaferrite

Here, we report a comprehensive study to explore the synthesis and comparative analysis of co-substituted M−type La3+/Cu2+ and La3+/Ni2+ hexaferrite (Sr1-xLaxFe12-xMxO19 where M = Cu and Ni; (x = 0.0, 0.05, 0.1, 0.15, and 0.2)) prepared through the sol–gel auto-combustion approach. X-ray diffraction (XRD) analysis shows both systems' single-phase structure of Sr hexaferrite. The structural parameters decreased as the number of substituted ions increasedas the crystal lattice contracts due to the smaller ionic radii being doped. Theaverage crystallite sizes were found using the Scherrer equation using the highest intensity peaks, and the results show nano-sized particles. The morphological structure of Sr-hexaferrite was studied using Field Effect Scanning Microscopy (FESEM). As a result, irregularly shaped particles with slight agglomeration are observed on the topography in both systems. Two absorption bands were observed in all synthesised samples' Fourier-transformed infrared spectroscopy (FTIR) spectra, supporting the ferrite's formation. These materials are a good option for high-density recording media. Both samples show high magnetic natures, which can be observed from the hysteresis loop. Overall, the room temperature magnetic parameters measured slightly increase as the dopant materials increase. The squareness ratio of the synthesizedsamples shows the uniaxial anisotropy with single magnetic domain particles. The Maxwell-Wagner and Koop model clarifies the reason the dielectric characteristics exhibit the typical behavior of ferrites.

Influence of magnetic external field and particle size on the formation of a single domain state

Magnetic particles are widely employed in applications ranging from medical to industrial. Their magnetic state, a single-domain versus a multi-domain configuration, depends on their size as well as the strength and frequency of an applied magnetic field. The critical size of a single-domain ferromagnetic/ferrimagnetic particle can be determined by minimizing the total free energy, which should include the Zeeman energy term when an external field is applied. To study the effect of an applied field on the critical size of single-domain particles as a function of their size, we performed numerical simulations using MuMax3 software for Fe, Co, Fe3O4, MgZn ferrites, and BaFe12O19. These materials exhibit a wide range of values for magnetic properties such as saturation magnetization and anisotropy. We determined the critical field at which a given sized particle becomes a single-domain magnetic particle. Our MuMax3 calculations for an iron spherical particle were compared with Kondorskii’s analytical theory.

High-frequency magnetic response of superparamagnetic composites of spherical Fe65Co35 nanoparticles

The response of composites of magnetic nanoparticles (MNPs) with randomly-oriented magnetocrystalline anisotropy axes to a linearly-polarized ac field or a rotating field is studied with regard to the concept of using superparamagnetic nanocomposites as core materials for high (sub-GHz and GHz) frequency power conversion devices. We perform micromagnetic simulations of systems of spherical 5nm-diameter nanoparticles of Fe65Co35 with two different concentrations arranged periodically within a dielectric matrix, including thermal fluctuations of the magnetization within the stochastic thermal field. Because the particles are closely packed, the effect of surface anisotropy is neglected. The dependence of the amplitude of the magnetic response function on temperature is determined. We show the inapplicability of Brown’s classic theory of thermal excitations in single-domain magnetic particles for given material parameters even in the absence of the magnetostatic field. Magnetostatic interactions of MNPs are found to be necessary for stabilizing the dynamical magnetic response in the high temperature (low-energy-barrier) range. They allow for driving magnetization oscillations at room temperature with amplitude comparable to the zero-temperature case. Dynamical (hysteretic and residual) losses are discussed.

Improving the efficiency of machine learning in simulating sedimentary heavy metal contamination by coupling preposing feature selection methods

Sediment cores were collected from Taihu Lake in China. The chronology was determined by radionuclide. Heavy metals and magnetic properties of each core slice were assessed, respectively. The concentrations of most heavy metals in sediments surged at 20 cm from the surface, accompanying the increase in the concentrations of single-domain magnetic particles. This may be resulted from the influence of anthropic activities on the lake's environment after the 1970s. Two feature selection methods, random forest (RF) and maximal information coefficient (MIC), were combined with support vector machine (SVM) model to simulate heavy metals, with the inclusion of selected magnetic and physicochemical parameters. Compared with the modeling results obtained with the full set of parameters, a reasonable simulation performance was obtained with RF and MIC. RF performed better than MIC by increasing the R2 of simulation models for Cd, Cr, Cu, Pb, and Sb. For heavy metals with high ecological risks (As, Cd, Cr, Hg, Pb, Sb), the correlation coefficients for observed and predicted data ranged from 0.73 to 0.97 with only 14–27% of the parameters selected by RF as input variables. The RF-RBF-SVM enabled heavy metal predictions based on the magnetic properties of the lake sediments.

Magnetic losses in single-domain magnetic particles

Magnetic losses in single-domain magnetic particles

A theoretical examination of localized nanoscale induction by single domain magnetic particles

Single domain magnetic nanoparticles are increasingly investigated as actuators of biological and chemical processes that respond to externally applied magnetic fields. Although their localized effects have often been attributed to nanoscale heating, recent experimental evidence suggests the need to consider alternative hypotheses. Here, using the stochastic Landau–Lifshitz–Gilbert equation and finite element modeling, we investigate and critically examine an alternative hypothesis that localized effects may instead involve the induced electric fields arising from the dynamical behavior of individual single domain magnetic particles. We model the magnetization dynamics and resulting induced electric fields for two relevant and distinct cases of magnetic nanoparticles in alternating magnetic fields: (1) magnetogenetic stimulation of channel proteins associated with ferritin and (2) catalytic enhancement of electrochemical hydrolysis. For the first case, while the local electric fields that ferritin generates are shown to be insufficient to perturb the transmembrane potential, fields on the surface of its mineral core on the order of 102–103 V/m may play a more plausible role in mass transport of iron ions that indirectly lead to stimulation. For the second case, our model indicates that the highest interfacial electric field strengths, on the order of 102 V/m, are expected during reversal events. Thus, nanoparticles well suited for hysteresis heating can also act as intermittent sources of localized induced electric fields in response to an alternating applied field. Finally, we compare the magnitude and timescale of these electric fields to technologically relevant phenomena, showing that they are generally weaker and faster.

Sonochemical synthesis of Mn0.5Zn0.5ErxDyxFe2-2xO4 (x ≤ 0.1) spinel nanoferrites: Magnetic and textural investigation

Mn0.5Zn0.5ErxDyxFe2-2xO4 (x ≤ 0.1) spinel nanoferrites (SNFs) were fabricated successfully via Ultrasonic irradiation. Structural and morphological analysis were investigated via X-ray diffraction diffractometer (XRD), scanning (SEM) and transmission electron microscopes (TEM), Fourier-transform infrared spectroscopy (FTIR), and Surface Area Analyzers (BET). XRD showed the formation of highly pure Mn-Zn spinel ferrite phase with an average crystallite size within 19–26 nm range. The formation of spherical nanoparticles with small particles size was also approved by SEM and TEM techniques. Magnetization response to the magnetic field applied (M vs H) and temperature and (M vs T under ZFC and FC modes), were investigated to understand the impact of Er and Dy co-doping mechanism on the magnetic features of MnZn SNFs. The findings through the magnetization measurements demonstrate superparamagnetic (SPM) behavior with single magnetic domain particles for different prepared products and with no coercivity (Hc) and remanence (Mr) at RT and at temperatures above the TB (blocking temperature). At lower temperatures below TB, it has been illustrated that the prepared SNFs have ferrimagnetic (FM) behavior with the existence of coercivity (Hc) and remanence (Mr). The calculated squareness (SQR = Mr/Ms) at T = 10 K are ranging between 0.14 and 0.29, which are below the predicted value of 0.5, reflecting the MMD nature in different prepared SFNPs at T = 10 K. In comparison to pristine product, the saturation magnetization (Ms) initially increased for lower co-doping contents of Er and Dy up to x = 0.04 and then decreased by the further Er and Dy co-doping concentrations (x > 0.04).

Impact of Gd substitution on the structure, hyperfine interactions, and magnetic properties of Sr hexaferrites

Gd3+-substituted nano-sized Sr-hexaferrite, SrGdxFe12-xO19 (0.00 ≤ x ≤ 0.05) NHFs (SrGd NHFs), were fabricated by a one-pot sol-gel combustion approach assisted by citric acid. The crystal structures, surface morphologies, magnetic properties, and hyperfine interactions of the calcined samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM (HR-TEM), vibrating sample magnetometry (VSM), and Mössbauer spectrometry. The oxidation states and chemical compositions of the NHFs were evaluated using XPS. The single-phase crystalline structures of all products were confirmed by XRD analysis. The average crystallite sizes determined from the peaks of the highest intensity using the Scherrer equation were between 38 and 50 nm. Using 57Fe Mössbauer spectroscopy data, the quadrupole splitting, hyperfine magnetic field, isomer shift, and line width variation of the products were determined. The Mössbauer spectra showed that octahedral (Oh) 12k and 2a sites were preferentially occupied by Gd3+ions. The Gd3+content was found to have no influence on the electron density around the Fe3+ions at any crystallographic site. The magnetization (M) versus magnetic field (H) data were collected at room (300 K) and ultra-low (10 K) temperatures. Neither the zero-field cooling (ZFC) nor field cooling (FC) mode plots of magnetization vs. temperature revealed any blocking temperature peaks. Both the M-H curves and FC-ZFC magnetization revealed ferrimagnetic behavior of the products. Furthermore, the FC-ZFC magnetization exhibited super-spin glass behavior at low temperatures. Reductions in the coercive field (Hc), saturation magnetization (Ms), and remanence (Mr) magnetization were achieved with Gd substitution of up to 0.03 into the hexaferrite system; however, with further increase in Gd content, these values started to increase. The calculated squareness ratio (Mr/Ms) revealed that all of the NHF samples were composed of single magnetic domain particles with uniaxial anisotropy.

Environmental magnetic properties of core sediments in the Yellow River subaqueous delta and their chronologicalapplications

The Yellow River has shifted frequently in the downstream region since 1885; it has flowed into the sea through the Qingshuigou channel from 1976 onward, thus forming the latest delta lobe (1976–present). During the past ~40 years, the sediment load of the Yellow River has been greatly reduced because of human and natural activities, such as reservoir construction, soil and water conservation, and river avulsion. Beginning in 2002, the water-sediment regulation scheme (WSRS) has also changed the sediment loading patterns of the Yellow River. Several studies have reported on the erosion and deposition characteristics of the latest lobe of the Yellow River Delta over the past several decades, based on remote sensing methods and water-depth measurements. However, continuous sedimentary records of delta erosion and deposition and their responses to natural and human activities in the watershed are lacking. Here, we obtained three sediments cores, YD01, YD02, and YD03, from the subaqueous delta of the latest lobe of the Yellow River Delta. These cores contain sediments deposited from 1976 to 2018. We analyzed the environmental magnetism and lithological characteristics of these cores, and investigated their responses to natural and human activities in the watershed of the Yellow River, as well as possible applications to sediment dating in the Yellow River Delta. The results show that frequency-dependent susceptibility ( χ fd%) and anhysteretic remanent magnetization susceptibility ( χ ARM) values were high in core sediments deposited from 1976 to 1996, indicating abundant contents of fine single-domain (SD) and superparamagnetic (SP) magnetic particles, and therefore a dominant sediment supply from the Chinese Loess Plateau. Small decreases in χ fd% and χ ARM in sediments deposited after 1986 revealed slight reduction of the sediment load from the Yellow River, which was likely caused by sediment retention related to the construction of the Longyangxia Reservoir. Rapid rises in χ fd% and χ ARM occurred in core YD01 sediments deposited during 2002 and ~2007, likely in response to the implementation of the WSRS, which resulted in an increase in sediment transportation. Increases in hard isothermal remanent magnetization (HIRM) values, an indicator of high-coercivity magnetic minerals such as goethite and hematite, in cores YD02 and YD03 from 2002 to ~2007 may also represent the start of the WSRS. This is because the downstream riverbed of the Xiaolangdi Reservoir underwent intense erosion during the implementation of the WSRS, leading to large-scale transportation of coarse sediments enriched in goethite and hematite, which were deposited on the riverbed before the implementation of the WSRS. The lack of increased contents of fine SD and SP magnetic minerals in cores YD02 and YD03 compared with YD01 in the interval deposited between 2002 and ~2007 was attributed to erosion and redeposition in the areas around cores YD02 and YD03. Large drops in SD and SP contents after ~2007 were detected in all three cores, revealing intense erosion near the river mouth likely caused by river channel shift and reduced capability of the WSRS to remove sediments. Contents of SD and SP particles increased again in sediments deposited after 2014 in cores YD02 and YD03, likely related to erosion of the present (after 1996) Yellow River mouth and transportation of fine particles to the region near cores YD02 and YD03. In summary, the magnetic parameters χ fd% and χ ARM and the lithological characteristics of cores YD01, YD02, and YD03 recorded sediment delivery changes caused by four events in the Yellow River watershed: The main river channel shift in 1976, construction of the Longyangxia Reservoir in 1986, the beginning of the WSRS in 2002, and weakened capability of the WSRS to remove sediments after ~2007. The notable changes of χ fd%, χ ARM, and lithology at the 1976, 1986, 2002, and ~2007 horizons may be used as dating points in future research of sediment cores from the Yellow River Mouth.

Optical Imaging of Magnetic Particle Cluster Oscillation and Rotation in Glycerol.

Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFeO) and iron oxide (FeO) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFeO particle clusters and 1.00 mg/mL for FeO particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 m, and the particle cluster diameter ranged from 5 to 45 m. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.

Microscale model of ferrogel samples with different polymer matrix structure

Ferrogels is a group of soft magnetically active composite materials with polymer gel (generally hydrogel) matrix filled by ferromagnetic colloid particles. Pronounced interrelation between magnetic and mechanical properties of ferrogels together with their biocompatibility make ferrogels attractive for various bio-medical applications. Evolution of ferrogel internal structure plays pivotal role in formation of unique magnetic mechanical behavior of ferrogel. Difficulty of direct observation on the structure scales enhances importance of theoretical (and numerical) study on ferrogels. The paper presents the results of modeling the behavior of a small ferrogel sample (up to 1000 magnetic particles) obtained using the method of coarse-grained molecular dynamics. The composite matrix is imitated by a quasi-regular mesh of ideal spring-beads chains, and single-domain magnetic particles with uniaxial anisotropy are placed in nodes of this mesh. The state of the sample is considered in the absence of external action, as well as in cycles of quasi-static magnetization for two variants of the topology of the polymer network (simple cubic and diamond-like), for different values of the magnetic moment of particles, their concentration, and anisotropy energy. Simulation has shown that samples with softer matrix (i.e. of diamond-like structure) demonstrate more noticeable magnetic deformation effects. The presence of magnetic anisotropy excites additional local stresses during particle moment reorientations, which complicates particles clustering and sample magnetization. Moreover, it has been found that anisotropy energy determines the character of the field induced change in the sample volume.

Molten salt synthesis, formation mechanism and greatly enhanced magnetic properties of randomly oriented BaM ferrite

Due to the influence of specific preparation process and product microstructure characteristics, it is a difficult task to prepare the randomly oriented BaFe12O19 (BaM) ferrite with large remanent magnetization (Mr) and high saturation magnetization (Ms), which hinder the practical application of the BaM ferrite. One of the means to solve this problem is to prepare well-developed hexagonal plate-like structure and single magnetic domain particles by lower synthesis temperature. In this study, the BaM ferrite were prepared using molten salt synthesis (MSS) method, and the preparation conditions of excellent magnetic properties and the formation mechanism of BaM ferrite synthesized by molten salt were discussed. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and magnetic properties analyses indicated that the BaM ferrite with greatly enhanced magnetic properties could be obtained by adjusting the calcination temperature, Fe3+/Ba2+ molar ratio and the salts to reactants mass ratio R. The Ms and Mr of the prepared BaM ferrite were 71.9 emu/g and 39.5 emu/g, respectively. The Ms of the prepared BaM ferrite was significantly enhanced, and the Mr was much higher than that of BaM ferrite prepared by other methods. Using hydrothermal method synthesized spindle-like α-Fe2O3 as a raw material confirmed that the formation mechanism of molten salt synthesis of BaM ferrite was dissolution and precipitation mechanism. The formation of BaM ferrite underwent a series of processes including BaFe2O4 and BaFe4O7 formation, iron oxide dissolution, BaFe2O4 and BaFe4O7 desolvation of Ba2+, ion diffusion, nucleation growth and precipitation.

Debye formulas for a relaxing system with memory

Rate (master) equations are ubiquitous in statistical physics, yet, to the best of our knowledge, a rate equation with memory has previously never been considered. We write down an integro-differential rate equation for the evolution of a thermally relaxing system with memory. For concreteness we adopt as a model a single-domain magnetic particle driven by a small ac field and derive the modified Debye formulas. For any memory time Θ the in-phase component of the resultant ac susceptibility is positive at small probing frequencies ω, but becomes negative at large ω. The system thus exhibits frequency induced diamagnetism. For comparison we also consider particle pairs with dipolar coupling. The memory effect is found to be enhanced by ferromagnetic coupling and suppressed by antiferromagnetic coupling. Numerical calculations support the prediction of a negative susceptibility which arises from a phase shift induced by the memory effect. It is proposed that the onset of frequency induced diamagnetism represents a viable experimental signature of correlated noise.

Enhancement of structural and magnetic properties of M-type hexaferrite permanent magnet based on synthesis temperature

The main purpose of this research work is to develop the single domain magnetic particles of M-type barium hexaferrite (BaFe12O19) using oxide precursors employing conventional powder metallurgy technique. The phase formation and magnetic performance of the powders and magnets will be optimized by adjusting calcination and sintering temperatures. The synthesis of M-type barium hexaferrite was carried out in two sections. A series of four samples have been prepared by initial wet mixed powders calcined at different temperatures, i.e., 750, 850, 950 and 1050 °C. On the basis of structural analysis, the sample calcined at 950 °C has been selected and further divided into four parts to sintered them at 1100, 1150, 1200 and 1250 °C. The structural measurements depict the confirmation of M-type barium hexaferrite structure. SEM micrographs show the hexagonal-shaped grains. The abrupt decrease in coercivity for the sample sintered at 1250 °C has been seen which may be due to high sintering temperature, at which the particles have multi-domain properties.

Switching probability of all-perpendicular spin valve nanopillars

In all-perpendicular spin valve nanopillars the probability density of the free-layer magnetization is independent of the azimuthal angle and its evolution equation simplifies considerably compared to the general, nonaxisymmetric geometry. Expansion of the time-dependent probability density to Legendre polynomials enables analytical integration of the evolution equation and yields a compact expression for the practically relevant switching probability. This approach is valid when the free layer behaves as a single-domain magnetic particle and it can be readily applied to fitting experimental data.

Magnetic properties of co-precipitated hexaferrite powders with Sm-Co substitutions optimized with the molten flux method

In this work, using the chemical coprecipitation method, Sr1−xSmxFe12−xCoxO19 (x = 0, 0.1, 0.2) hexaferrite powders were prepared. Major magnetization loops were recorded at room temperature in order to determine the correct calcination temperature for optimum hard magnetic properties. It is found that a small degree of substitution increases substantially the coercive field. Also, the use of the molten flux calcination method increases the remanent magnetization. SEM/EDXS and XRD measurements were performed at the calcined powders: the results show that a single hexaferrite phase is formed and that the substituted powders consist of an assembly of grains with a mean diameter of 40nm. Measurements of minor magnetization loops and of the temperature and time dependence of the magnetization confirm that the powders consist of a non-oriented single domain magnetic particles assembly. The results indicate that Sm could be a viable replacement for La in the manufacturing of hexaferrites with a high-energy product.

Micromagnetic simulation of two-body magnetic nanoparticles

Field-induced magnetization dynamics was investigated in a system of two magnetic nanoparticles with uniaxial anisotropies and magnetostatic interaction. By using the micromagnetic simulation, ultralow switching field strength was found when the separation distance between the two particles reaches a critical small value on nanometer scale in the perpendicular configuration where the anisotropic axes of the two particles are perpendicular to the separation line. The switching field increases sharply when the separation is away from the critical distance. The same results were observed when varying the radius of particles. The micromagnetic results are consistent with the previous theoretical prediction where dipolar interaction between two single-domain magnetic particles was considered. Our present simulations offered further proofs and possibilities for the low-power applications of information storage as the two-body magnetic nanoparticles could be implemented as a composite information bit.

The fcc/bcc phase transition in FexNi100−x nanoparticles resolved by first-order reversal curves

One-pot polyol processing was successfully used for the preparation of FexNi100−x nanoparticles. By increasing Ni concentration in FexNi100−x alloy, the phase transition from bcc to fcc crystalline structure was clearly indicated by the XRD data as well as the measured hysteresis loops. FORC diagrams demonstrated that the prepared samples consist of single-domain magnetic particles with a uniform particle size. By changing the molar ratio of the precursors, different compositions of FeNi alloy were obtained. The influence of the temperature, solvent, surfactant, and amount of NaOH was also studied on the particle size, structure, and magnetic properties of the products.

Chaotic dynamics of a magnetic particle at finite temperature

In this work, we study nonlinear aspects of the deterministic spin dynamics of an anisotropic single-domain magnetic particle at finite temperature modeled by the Landau-Lifshitz-Bloch equation. The magnetic field has two components: a constant term and a term involving a harmonic time modulation. The dynamical behavior of the system is characterized with the Lyapunov exponents and by means of bifurcation diagrams and Fourier spectra. In particular, we explore the effects of the magnitude and frequency of the applied magnetic field, finding that the system presents multiple transitions between regular and chaotic states when varying the control parameters. We also address the temperature dependence and evidence that it plays an important role in these transitions, almost suppressing the chaotic behavior close to the Curie temperature. Finally, we find that the system has hyperchaotic states for specific values of field and temperature.