Coercive Field Hc Research Articles

The Structural, Magnetic, and Transport Properties of the Pulsed Laser‐Deposited Co2FeAl Thin Films

Pulsed laser deposition (PLD)‐grown Co2FeAl (CFA) thin films on MgO(001) substrates are investigated in terms of structural, magnetic, and transport properties. The crystal structure of CFA thin films is changed from disordered A2 to partly ordered B2 structure, as the substrate temperature (Ts) increases from 600 to 700 °C, and both the saturation magnetization Ms and the coercive field Hc are enhanced with increasing Ts. Different from the CFA thin films prepared by magnetron sputtering, longitudinal resistivity shows a local minimum near 20 K for all the films due to a weak localization effect, and this type of low‐temperature anomaly is weakened with the improvement of structure ordering. Moreover, the origin of anomalous Hall effect (AHE) in CFA thin films is dominated by intrinsic mechanism, and the scattering‐independent intrinsic parameter is enhanced with the increase of Ts due to the improvement of crystal structure.

Effect of mechanical milling on magnetic, dielectric and magneto-electric properties of Z- type (Ba, Sr) hexaferrites

The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.

Influence of divalent metal ion (Zn2+) on magnetic properties, curie temperature and DC electrical properties in Ce3+ substituted Ni-Zn ferrites

Nanoparticles of Ni1−xZnxCe0.1Fe1.9O4 ferrite substituted with Zn2+ ion concentrations (0.0, 0.2, 0.4, 0.6, 0.8 & 1.0) have been synthesised via aqueous citrate precursor auto combustion method. The obtained Powder x-ray diffraction data suggests a good crystalline phase; the crystallite size exists in the range of 14 ∼ 38 nm. The lattice constant of samples increases with Zn2+ concentration. It validates Vegard’s law and the decreasing trends in porosity of the samples were identified. The inhomogeneity in the grains was confirmed from FE-SEM. The EDS spectrogram attributes the good stoichiometry in the product. The Thermogravimetric analysis reveals that the crystallization occurred within the temperature 800 °C. The high-temperature DC conductivity of the samples shows that NTC behaviour. The Curie temperature and activation energy are estimated and the activation energy of carriers are found to be more at the paramagnetic region. The magnetic saturation (‘Ms*’) has maximum for Zn2+ = 0.2 (57.7 emu g−1) and coercive field (Hc) related with a radius of occupancy of Zn2+ ion validates the relation and also, the value of the remanence ratio suggests that isotropic magnetization took place in the heterogeneous material.

Tailoring Magnetic and Transport Anisotropies in Co100−x–Cux Thin Films through Obliquely Grown Nano-Sheets

The magnetic and transport properties of pulsed laser-deposited Co100−x–Cux thin films were tailored through their nano-morphology and composition by controlling for the deposition geometry, namely normal or oblique deposition, and their Cu content. All films were composed of an amorphous Co matrix and a textured growth of Cu nanocrystals, whose presence and size d increased as x increased. For x = 50, all films were superparamagnetic, regardless of deposition geometry. The normally deposited films showed no in-plane magnetic anisotropy. On the contrary, controllable in-plane uniaxial magnetic anisotropy in both direction and magnitude was generated in the obliquely deposited films. The magnetic anisotropy field Hk remained constant for x = 0, 5 and 10, Hk ≈ 35 kAm−1, and decreased to 28 and 26 kAm−1 for x = 20 and 30, respectively. This anisotropy had a magnetostatic origin due to a tilted nano-sheet morphology. In the normally deposited films, the coercive field Hc increased when x increased, from 200 (x = 0) to 1100 Am−1 (x = 30). In contrast, in obliquely deposited films, Hc decreased from 1500 (x = 0) to 100 Am−1 (x = 30) as x increased. Activation energy spectra corresponding to structural relaxation phenomena in obliquely deposited films were obtained from transport property measurements. They revealed two peaks, which also depended on their nano-morphology and composition.

FeZrN Films: Magnetic and Mechanical Properties Relative to the Phase-Structural State.

The paper presents results of investigation of Fe65.3–100Zr34.7–0N7.5–0 films prepared by dc magnetron deposition on glass substrates and subsequent 1-hour annealing at temperatures of 300–600 °C. The influence of the chemical and phase compositions and structure of the films, which were studied by TEM, SEM, XRD, and GDOES, on their mechanical properties determined by nanoindentation and static magnetic properties measured by VSM method is analyzed. The studied films exhibit the hardness within a range of 14–21 GPa, low elastic modulus (the value can reach 156 Gpa), and an elastic recovery of 55–83%. It was shown that the films are strong ferromagnets with the high saturation induction Bs (up to 2.1 T) and low coercive field Hc (as low as 40 A/m). The correlations between the magnetic and mechanical properties, on one hand, and the chemical composition of the films, their phase, and structural states as well, on the other hand, are discussed.

Self-biased coplanar circulator based on electrochemically grown ferrimagnetic nanowires

This paper is about a self-biased coplanar circulator. The design approach is based on the use of magnetic composite substrates self-polarized made from ferrimagnetic nanowires. It consists of integrating and orienting cobalt ferrite (CoFe2O4) nanocrystallites in porous alumina membrane using the magneto-electrodeposition technique. XRD, SEM and EDX analysis confirmed the formation of the spinel phase of cobalt ferrite with a good distribution of Co, Fe and O elements in the unit cell of CoFe2O4 nanowires. The performed SQUID-VSM measurements have revealed that the nano-composite electrodeposited and cooled under a magnetic field of 0.6 T has the best magnetic properties, i.e. a large anisotropy field (Ha), moderate coercive field (Hc), and partial squareness ratio (Mr/Ms). This nano-composite has been selected as an interesting candidate for the fabrication of a miniaturized self-biased circulator. The study has started with the implementation of an analytical dimensioning process based on Bosma's theory. Based on interesting HFSS simulation results, a first prototype was fabricated in the clean room and characterized at high frequencies. The measurements of the S parameters have highlighted a circulation phenomenon of 3 dB.

Giant hysteretic effect in layered organic-inorganic hybrid magnets incorporating hydroxide and cinnamate layers

Layered organic-inorganic hybrid magnets, Co(cin)0.8(OH)1.2 (cin = cinnamate) (1) and Cu(cin) (OH) (2), have been synthesized by using a low energy process that employs transition metal nitrates as inorganic precursors and a cin as an organic precursor. The X-ray diffraction patterns and TEM images for the reaction products suggest that they possess organic-inorganic layered structure, where a transition metal hydroxide inorganic monolayer alternates with double cinnamate organic layers along the stacking direction. The compound 1 exhibits a ferrimagnetic long-range ordering (TC = 47.5 K) and large hysteresis with the coercive field Hc = 38 kOe. In contrast, the compound 2 shows soft ferromagnetic properties at low temperatures and a ferromagnetic phase transition occurs at TC = 15 K.

Graphdiyne doped with transition metal as ferromagnetic semiconductor

Long-range ferromagnetic ordering in semiconductors has become an attractive research hotspot due to its promising potential in spintronics and information technology. Especially the appearance of carbon-based semiconductors represented by graphdiyne (GDY) makes it easy to realize ferromagnetic semiconductors. Herein, a convenient and effective route has been developed to prepare GDY-based magnetic semiconductors using the modification with transition metal elements including Fe, Co, and Ni, respectively. Among them, lightly doped GDY with Co (Co-GDY) exhibits the most outstanding ferromagnetism with a typical Curie's temperature above room temperature. Meanwhile, the coercive field Hc = 78 Oe at T = 300 K of Co-GDY is the smallest, demonstrating characteristics of easy magnetization. Subsequent spin-polarized DFT calculation results reveal that the robust ferromagnetism of Co-GDY arises from the most significant local magnetic moment. Significantly, a noticeable band gap can still be maintained due to the very light doping level. These results reveal an optimization strategy for selecting doping elements, promoting carbon-based semiconductors application in spin-related fields.

The Effect of Arrive Angle of External Magnetic Field on The Shape of Hysteresis Curve Permalloy Ni80Fe20 By Simulation

Magnetic sensor is a type of sensor that utilizes changes in resistance caused by changes in the magnetic field H or B. One of the suitable magnetic materials to be used as a study material for making magnetic sensors is permalloy Ni80Fe20. The reading error of the magnetic sensor of the Ni80Fe20 permalloy material affects hysteresis curve of the material and requires correction of the angle of incidence of the external magnetic field in order to provide accurate results on the storage media. In this our current research using Finite Difference OOMMF, we investigated the effect of the angle of incidence of the external magnetic field (H) on the hysteresis curve was carried out on an application based on. The research was conducted by reviewing the parameter literature of the Ni80Fe20 permalloy material and then compiling it in a script and simulating it on an application based on Finite Difference OOMMF. The data obtained from the simulation are normalized magnetization (m), external magnetic field H and coercivity field (Hc) which have been influenced by the angle of incidence. The results of the hysteresis curve at a size of 5 nm with a variation of the angle of incidence 0o are indicated by the value of the external magnetic field H of 10000 mT to -10000 mT with a coercive field Hc of 5000 mT to -5000 mT. The normalized magnetization value m is 1 to -1. The variation of the angle of incidence of 30o produces a coercive field Hc of -108.3 mT to 108.3 mT and a normalized magnetization of 0.86 to -0.86. The 45o incident angle variation produces a coercive field Hc -88.4 mT to 88.4 mT and a normalized magnetization of -0.7 to 0.7

Evaluation of effective magnetic anisotropy constant of magnetic nanoparticles from coercive field of AC magnetization curve

Magnetic nanoparticles (MNPs) have been widely studied for use in biomedical application with the magnetic anisotropy constant K playing an important role in determining the performance. We estimated K near room temperature from the coercive field Hc of an AC magnetization (M–H) curve. First, we performed numerical simulation of the AC M–H curve of immobilized MNPs and clarified the dependencies of Hc on the MNP parameters and excitation conditions. Based on the simulation result, we obtained an analytical expression for Hc that was more general and included the previously obtained expression; and in addition, it could be applied to an MNP sample with a core-size distribution. Next, we measured the AC M–H curves of two commercial MNP samples and determined the dependencies of Hc on the amplitude and frequency of the excitation field. The dependencies agreed reasonably well with the analytical results. The K value was evaluated to obtain the best fit between the measured and analytical Hc, and the obtained K values were consistent with those estimated using other methods. The temperature dependence of K near room temperature was also determined. The present method will provide a useful tool to estimate the K value of MNPs.

Increased room temperature ferromagnetism in Co-doped tetrahedral perovskite niobates.

Dilute magnetic semiconductors (DMSs), such as (In, Mn)As and (Ga, Mn)As prototypes, are limited to III–V semiconductors with Curie temperatures (Tc) far from room temperature, thereby hindering their wide application. Here, one kind of DMS based on perovskite niobates is reported. BaMxNb(1−x)O3−δ (M = Fe, Co) powders are prepared by the composite-hydroxide-mediated method. The addition of M elements endows BaMxNb(1−x)O3−δ with local ferromagnetism. The tetragonal BaCoxNb(1−x)O3−δ nanocrystals can be obtained by Co doping, which shows strong saturation magnetization (Msat) of 2.22 emu g−1, a remnant magnetization (Mr) of 0.084 emu g−1 and a small coercive field (Hc) of 167.02 Oe at room temperature. The ab initio calculations indicate that Co doping could lead to a 64% local spin polarization at the Fermi level (EF) with net spin DOS of 0.89 electrons eV−1, this result shows the possibility of maintaining strong ferromagnetism at room temperature. In addition, the trade-off effect between the defect band absorption and ferromagnetic properties of BaMxNb(1−x)O3−δ is verified experimentally and theoretically.

Alterations in the magnetic and electrodynamic properties of hard-soft Sr0.5Ba0.5Eu0.01Fe12O19/NixCuyZnwFe2O4 nanocomposites

Hard/soft (H/S) Sr0.5Ba0.5Eu0.01Fe12O19/NixCuyZnwFe2O4 nanocomposites (NCs) were produced via a one-pot sol–gel auto-combustion procedure. Phase and surface analyses were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Magnetization measurements for H/S NCs with different x, y, and w ratios were investigated at two different temperatures (300 and 10 K). The M−H curves were not smooth for the different H/S NCs, revealing that the exchange interaction was incomplete. The derivative of the magnetization (dM/dH versus H) exhibited two separate peaks, confirming the non-coupled H/S mixtures. Maximum saturation magnetization (Ms) values of 93.9 and 63.1 emu/g were obtained at 10 and 300 K, respectively, for the H/S Sr0.5Ba0.5Eu0.01Fe11.99O19/Ni0.3Cu0.3Zn0.4Fe2O4 NC, which contained the highest content of Zn and the same contents of Ni and Cu within the soft magnetic phase. The calculated squareness ratios (SQR = Mr/Ms) were less than 0.5, indicating incomplete exchange coupling. The coercive field (Hc) of the produced NCs reached a maximum value of approximately 2485 Oe at 300 K and 2331 Oe at 10 K with a decrease in the Ms values to 56.9 emu/g at 300 K and 78.5 emu/g at 10 K for the H/S Sr0.5Ba0.5Eu0.01Fe11.99O19/Ni0.8Cu0.1Zn0.1Fe2O4 NC, which contained lower fractions of Zn and Cu and the highest fraction of Ni. The reflection/transmission-based waveguide approach was employed to investigate the electrodynamic properties of the H/S NC samples within a frequency band of 7–18 GHz. The reflection and transmission coefficients (S11/S21) were measured using a vector network analyzer (VNA) for the sample placed inside a waveguide. The frequency dispersions of the magnetic permeability and electric permittivity were calculated.

Room temperature short-range ferromagnetic order in Ni-doped tetragonal perovskite niobate

Here, we report a strong room-temperature magnetism in Ni-doped BaNbO3. The tetragonal BaNixNb(1-x)O3-δ nano-powders are prepared by the composite-hydroxide-mediated method. The as-prepared BaNixNb(1-x)O3-δ has a saturation magnetization (Msat) of 2.54 emu/g, a remnant magnetization (Mr) of 0.228 emu/g, and a small coercive field (Hc) of 99.14 Oe at room temperature, presenting as a short-range magnetic order. The Ni-doping leads to an incommensurate valence state of Nb, and the oxidation state of Ni in the matrix is + 2. It brings not only strong local spin polarization to the matrix, but also balances the oxygen defects and gives rise to a more doping content. The strong magnetism originated from the existence of short-range magnetic order and the strong local net spin polarization at the Fermi level (EF), which are proved by the first-principle calculations.

Etching damage induced performance degradation in spin transfer torque magnetic random access memory fabrication

Damage mechanisms and related performance degradations induced by ion beam etching (IBE) process in the fabrication of magnetic tunnel junctions (MTJs) were studied systematically. The loss in tunneling magnetoresistance (TMR) and coercive field (Hc) was investigated with different MTJ pillar sizes and IBE incident angles. It is found that IBE-induced damage is the formation of a surficial amorphous shell in the outer rim of an MTJ pillar. This amorphous shell is of low conductivity and TMR, mainly arising from the lattice damage of MgO barrier and partial oxidation of free/reference layers. Based on experimental and theoretical findings, we optimized the IBE process to reduce the damage as well as recover from degradation. As a result, the TMR loss ratio in comparison with a blanket film is reduced from about 18% to 7%, and Hc is increased from 1490 to 2280 Oe for the same stack.

Study the effect of symmetrical voltage of electrodeposition and annealing ‎temperature on magnetic properties of Fe-Sn alloy nanowires

In this research, the Fe-Sn alloy nanowires were made by AC electrodeposition method in anodic ‎aluminum oxide (AAO). The effect of different symmetrical voltages of electrodeposition (17.5-32.5 V) ‎and annealing temperature on magnetic and structural properties of Fe-Sn nanowires were investigated. ‎The magnetic properties, morphology, element composition of materials and crystal structure of the ‎nanowires were studied by AGFM, SEM, EDX and XRD, respectively. The results showed that, coercivity ‎field (Hc) and square ratio (Sq) increases by increasing deposition voltage and also, crystallinity of the ‎nanowires and resulting their crystalline magnetic anisotropy increased, but deposition percentage of Sn ‎to Fe reduced. The Hc and Sq of prepared nanowires were increased by annealing due to increases in their ‎crystalline structure and crystalline magnetic anisotropy. The most variation in Hc and Sq were achieved ‎for prepared nanowires at 30 V.‎

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.

Studying structural, magnetic and morphological features of electrochemically fabricated thin films of Co–Ni–Fe with different Fe compositions

In this work, a detailed study on the influence of the Fe composition on the crystallite size, lattice parameter, crystallographic texture, coercive field (Hc), magnetic squareness ratio (SQR), domain structure, surface roughness and grain size in electroplated Co–Ni–Fe deposits was carried out. For this aim, Co–Ni67, Co–Ni61–Fe6 and Co–Ni54–Fe13 thin films with different Fe compositions were fabricated using electrochemical deposition technique. The results showed that the composition of Fe in the deposit depends on the concentration of Fe ions in the electroplating solution. An increase in the Fe composition caused a noticeable reduction in the size of crystallites and induced a considerable enhancement in the strength of the preferred orientation being in the [111] direction. It was also observed that an increase in the Fe composition makes the lattice parameter larger. Compared to other deposits, the Co–Ni54–Fe13 with the highest Fe composition exhibited a lower surface roughness and a more compact nodular surface topography consisting of relatively finer grains. All deposits displayed a stripe domain (SD) structure, an in–plane magnetic hysteresis loop with a vertical magnetization component and a semi–hard magnetic property. However, the Hc value, SQR parameter and SD width varied in accordance with the Fe composition.

Preparation of Co-Fe-Ni alloy micropillar by microanode-guided electroplating

Microanode-guided electroplating (MAGE) was performed to prepare cobalt-iron-nickel alloying micropillars. The electrolyte was prepared by fixing [Fe2+] at 0.040 M and varying [Co2+] in 0.040–0.100 M and [Ni2+] in 0.30–0.60 M. The effect of bath composition on the compositional, mechanical, and magnetic properties of the alloying micropillars was investigated. Resulting from FE-SEM and EDS, all the micropillars demonstrated a smooth morphology but in different compositions depending on the bath composition. Through XRD analysis, the micropillars were characterized in nanocrystals of Co-Ni and Co7Fe3. After nano-indentation testing, the reduced Young’s modulus of the pillars was estimated at 103.1–185 GPa and the hardness at 5.70–6.38 GPa. Investigation of all the specimens with VSM, Co61Fe27Ni12 and Co63Fe25Ni12 displayed the notable saturation magnetization (Ms = 180 and 175 emu/g) and the lowest coercive magnetic field (Hc = 2.1 and 1.4 Oe) among them. The mechanism of anomalous Co-Fe-Ni electrodeposition is proposed.

Preparation and structural investigation of Polyethylene glycol (PEG) / nano-ferrite composites

Polyethylene glycol (PEG)/nano-ferrite composites have been prepared by using CoFe2O4, CuFe2O4, Co0.5Cu0.5Fe2O4 and MgFe2O4 ferrite nano-particles synthesized by citrate precursor method along with PEG with different percentages. Ferrite samples have been characterized by X-ray diffraction (XRD) to confirm the formation of pure spinel ferrite phase and, transmission electron microscopy (TEM) to ensure that the average particle size is within the nano-scale. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) thermographs of the ferrite samples have been used to ensure the complete formation of pure ferrites at temperatures above 800oC. The ferrites and their composites with PEG, have been investigated by FTIR spectroscopy. The main bands of ferrites and PEG have been clearly displayed in agreement with literature. A systematic shift of the bands has been observed upon adding PEG. The magnetic properties have been explored by using the vibrating sample magnetometer (VSM). Where the values of of saturation magnetization (Ms), remnant magnetization (Mr) and coercive field (Hc) for pure ferrite and composite samples vary with the presence of different divalent cations which have different magnetic moment. Whereas, Hc values remain constant as obtained in pure ferrites regardless the ratio of PEG. The obtained values of Hc are comparable with those in literature, which can be used in electromagnetic wave attenuation.

Effect of Ti doping on the structural, morphological and magnetic properties of La0.7Ga0.3Fe1-xTixO3

Orthoferrites perovskites are an important family of materials in the field of nanotechnology, particularly for cathodes in solid oxide fuel cells. Doping these materials enables the enhancement and control of their properties. In this context, we studied the effect of Ti doping on different properties of the La0.7Ga0.3Fe1-xTixO3 (x = 0, 0.1, 0.2 and 0.3) lanthanum orthoferrites. X-Ray Diffraction (XRD) measurements proved the presence of two orthorhombic phases with Pbnm and Pnma space groups. SEM images corroborate the XRD results, clearly signaling the presence of two phases in these samples, with EDS analysis allowing the estimation of each phase fraction. FTIR and Raman spectroscopies allowed us to study the vibrational modes related with the La-O, Fe-O and Ti-O bonds. We note a shift towards higher wavenumber associated with the increase in Ti. Magnetic measurements showed a transition from antiferromagnetism to weak ferromagnetism with the introduction of Ti. The zero-field cooled (ZFC) and field cooled (FC) magnetization versus temperature curves do not superimpose, proving the heterogeneity of the magnetic properties of the samples. The saturation magnetization Ms, the remanent magnetization Mr and the coercive field Hc decrease with both increasing temperature and Ti content.