Maximum Coercivity Research Articles

A sustainable approach for the synthesis of PbFe12O19 materials using tomato pulp as a fuel: Structural, morphological, optical, magnetic, and dielectric traits

Herein, a PbFe12O19 (PbM) nanostructured material was prepared using novel Tomato pulp fuel via the sol–gel auto-combustion technique. The synthesis of PbM is reported for the first time using tomato pulp, which acts as an eco-friendly chelating agent, reducing agent and natural fuel. The XRD patterns of PbM samples (T0, T1, T2, T3, T4, T5) except T4 contains additional phases of PbO. The FESEM images indicated the lowest grain size of 355 nm for the T1 specimen, whereas the T0 and T4 specimens acquired a grain size of 1380 and 883 nm respectively. However, the FESEM images of produced samples showed irregularly shaped grains with distinct grain boundaries and agglomerated nature. The maximum coercivity (Hc) and saturation magnetization (Ms) of 1429 Oe and 58.3 emu/g were observed for the T4 specimen. Therefore, the synthesized nanohexaferrites can be a beneficial candidate for the microwave absorber and high-density recording media. In addition, the dielectric constant and dissipation factor concede a diminishing behavior with the increase in frequency. Thus, hexaferrite with such dielectric behavior is beneficial for microwave and switching device applications.

Synergistically tailoring the microstructure and chemical heterogeneity of nanocrystalline multi-main-phase Nd–Ce–Fe–B magnet: Critical role in magnetic performance

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (Ts). An optimum Ts of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at Ts = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity Hcj, the preferable remanence Br, and the resultant optimum maximum energy product (BH)max, which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher Ts leads to the inferior magnetic properties. At lower Ts below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher Ts above 700 °C, the decreased Hcj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and Ts, concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets.

Exploring the structural and magnetic trends in Ba0.9Sm0.1Fe12−xAlxO19 M-type Hexaferrites

The current study describes the structural and magnetic properties of Ba0.9Sm0.1Fe12−x Al x O19 (x = 0.0, 0.5, 1.0, 2.0, 3.0) M-type hexaferrites. The conventional ceramic route was implied to prepare all the nominal samples. Morphological analysis suggested the non-presence of secondary phases as well as the formation of the hexaferrites material. X-ray Diffraction technique was used for structural analysis from which microstructural parameters are calculated and discussed. Magnetic properties are measured at room temperature. The saturation magnetization (Ms) and coercivity (Hc) values show a cyclic and converse trend for synthesized samples. Firstly, a decrease in Ms and an increase in Hc was observed up to intermediate dopant incorporation and becomes converse for higher doping levels. The maximum coercivity and minimum magnetization are observed for Ba0.9Sm0.1Fe11Al1O19. The c/a and Mr/Ms ratio suggest the formation of perfect M-type hexaferrites. This work suggests that synthesized material is a good option for magnetic applications e.g., transformer and inductor cores, microwave devices, recording heads, and magnetic shielding.

Super-high coercivity NdFeB magnet fabricated with double Tb-rich/lean shells by double alloy method and grain boundary diffusion

In this work, the high performance NdFeB magnet were fabricated by double alloy method and grain boundary diffusion Tb70Cu20Ga10 alloys. The maximum energy product (BH)max and coercivity Hcj of the magnet are 45.33 MGOe and 35.46 kOe, respectively. The reversible temperature coefficients of coercivity of the diffusion magnets improve from − 0.456%/°C to − 0.412%/°C at the range of 22 °C −180 °C. The magnetostatic loss of NdFeB magnet was analyzed in high temperature applications by general finite element method (FEM). The RE-(Fe,CuGaO) grain boundary phases and double Tb-rich/lean shells improve the utilization rate of heavy rare earths and coercivity of magnets after diffusion. The magnetization reversal mechanism of double core-shell microstructures had been discussed. This work may shed light on developing coercivity above 30 kOe of NdFeB magnet with low heavy rare earth through modified microstructure.

3D Printing of PLA/Magnetic Ferrite Composites: Effect of Filler Particles on Magnetic Properties of Filament

Three-dimensional printing is one of the most promising areas of additive manufacturing with a constantly growing range of applications. One of the current tasks is the development of new functional materials that would allow the manufacture of objects with defined magnetic, electrical, and other properties. In this work, composite magnetic filaments for 3D printing with tunable magnetic properties were produced from polylactic acid thermoplastic polymer with the addition of magnetic ferrite particles of different size and chemical composition. The used magnetic particles were cobalt ferrite CoFe2O4 nanoparticles, a mixture of CoFe2O4 and zinc-substituted cobalt ferrite Zn0.3Co0.7Fe2O4 nanoparticles (~20 nm), and barium hexaferrite BaFe12O19 microparticles (<40 µm). The maximum coercivity field HC = 1.6 ± 0.1 kOe was found for the filament sample with the inclusion of 5 wt.% barium hexaferrite microparticles, and the minimum HC was for a filament with a mixture of cobalt and zinc–cobalt spinel ferrites. Capabilities of the FDM 3D printing method to produce parts having simple (ring) and complex geometric shapes (honeycomb structures) with the magnetic composite filament were demonstrated.

Influence of Ce-Mn co-doping on the structure and magnetic properties of cobalt ferrites

In this study, we selected Ce3+ and Mn2+ as co-doped ions in order to improve the magnetic properties of cobalt ferrite. The nominal composition Co1−xMnxFe2−xCexO4 (x = 0, 0.05, 0.10, and 0.20) nanoparticles were prepared by facile co-precipitation technique, and the effect of co-doping content on the structural and magnetic properties of cobalt ferrite was investigated. The structural result confirmed the formation of cubic spinel structure for all co-doped samples, although secondary phase of CeO2 was detected in the high co-doping content ones. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bonding. All samples exhibited two frequency bands corresponding to the phonon vibrational stretching in the octahedral and tetrahedral lattice positions, respectively. The surface morphology analysis revealed the spherical shape of the ferrite nanoparticles. After co-doped with Ce3+ and Mn2+ ions, the magnetic parameters of cobalt ferrite were significantly improved. The maximum magnetization saturation is 66.5 emu/g when x = 0.05, and the maximum coercivity is 2288 Oe when x = 0.10. The two values are approximately 29% and 47% higher than that of the un-doped one. At the same time, the maximum energy product reaches 0.72 MG·Oe, which is about 118% higher than that for pure cobalt ferrite, i.e. 0.33 MG·Oe. The reasons may be related to the substitution of Fe3+ and Co2+ with Ce3+ and Mn2+, and also the resulting changes in crystallite sizes of the samples. These results demonstrate the effectivity of Ce-Mn co-doping in improving the magnetism of cobalt ferrite.

Synthesis and characterization of Ca substituted Ni-Zn nanoferrites- microstructural, magnetic and dielectric analysis

A series of cubic spinel structured, nanocrystalline and monophasic samples of the composition CaxNi0.4Zn0.6−xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) samples were synthesized via a chemical citrate precursor route, sintered at 700 °C. Raman and X-Ray Diffraction (XRD) investigations confirmed the single-phase cubic spinel configuration of the nanoferrites. A study of linearly fitted Williamson-Hall plots obtained using XRD data revealed the spinel structure of the prepared samples with the minute structural disorder wherein low values were estimated for lattice strain, ε, (0.003 × 10−3 −1.66 ×10−3) and dislocation density, δ, (0.665 × 10−3-1.73 × 10−3) for different Ca concentrations. The nanoferrites of Ca-doped Ni-Zn were found to be highly magnetic when subjected to a maximum applied field of 20 kOe under VSM investigations. Nanoferrite composition with x = 0.4 exhibited the maximum magneto-crystalline anisotropy constant (11452), remanent magnetization (22 emu/g), and coercivity (199.91 Oe) while maximum saturation magnetization (65.27 emu/g) and magnetic moment (2.756 μB) were found for the Ca0.1Ni0.4Zn0.5Fe2O4 composition. The samples were synthesized to explore their utilization in storage devices and high-frequency devices.

Unexpected Coercivity Enhancement >1T for Nd-Fe-B Permanent Magnets With 20 wt% Nd Produced by Laser Powder Bed Fusion

The impact of laser powder bed fusion (LPBF) on coercivity of Nd-lean commercial MQP™-S powder is investigated. It is found that different processing parameters, such as laser power, scan velocity, and hatch spacing, have a remarkable impact on the magnetic performance of LPBF-processed Nd–Fe–B permanent magnets. The increase of energy input during manufacturing will also increase coercivity and a maximum value of 920 kA/m ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{0}H_{c} =1.15$ </tex-math></inline-formula> T) was achieved without any further post-processing. Among other parameters, hatch spacing was identified as the major contribution to coercivity and its role is discussed on basis of the several re-melting events if hatch spacing becomes increasingly smaller than the laser focus diameter. The maximum coercivity is obtained, for hatch spacing of 35 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and laser focus diameter of 110 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , which led to a threefold re-melting of the sample.

Influence of Gd content on the structural, Raman spectroscopic and magnetic properties of CoFe2O4 nanoparticles synthesized by sol-gel route

The structural and magnetic properties of sol-gel synthesized Gd doped (x = 0.00 to 0.15) CoFe2O4 nanoparticles (NPs) have been studied. The x-ray diffraction (XRD) and FTIR spectroscopy along with Raman spectra confirmed the formation of face centered cubic inverse spinel structure. TEM images showed the NPs are well-dispersed with average particle size 30 nm. Room temperature magnetic measurement showed the value of coercivity fluctuates from 353 Oe to 1060 Oe for different % of Gd content. The maximum coercivity, saturation magnetization, magnetic moment, magnetic anisotropy, remnant magnetization found for 0.03% Gd content are 1060.19 Oe, 77.53 emu/gm, 3.29 μ, 4.11 × 104 erg/cm3, 32.38 emu/gm, respectively. The large value of coercivity indicated that the interparticle interactions and crystalline anisotropy are high. Thus CoFe2-xGdxO4 magnetic NPs might be a potential candidate for data processing, automotive and telecommunications.

Preparation of anisotropic (Ce, Nd, Pr)-Fe-B powder with HDDR method from wasted sintered magnets

With the wide application of Ce-contained rare earth (RE) permanent magnets, recycling of wasted Ce-contained magnets has drawn more and more attention. Hydrogenation-disproportionation-desorption-recombination (HDDR) method was used to prepare anisotropic magnetic powder from wasted (Ce, Pr, Nd)-Fe-B sintered magnet (N45 magnet). The influence of hydrogen pressure in disproportionation (Pdis) and desorption (Pdes) and the disproportionation time (tdis) on the magnetic properties and microstructures of HDDR powders was studied. The Pdis, Pdes and tdis were optimized to be 50 kPa, 5 kPa and 5 h, respectively. The optimized anisotropic HDDR (Ce, Pr, Nd)-Fe-B powder possessed the coercivity of 10.15 kOe, remanence of 11.14kG and the degree of alignment of 0.77. This coercivity has reached 83 % of that of the recycled N45 magnet. Microstructure examination with scanning electron microscope revealed that the optimized HDDR powder is consisted of flake-shaped particles with hierarchical structure. The distribution of rE-rich phase has been significantly influenced by Pdis, Pdes and tdis. The optimized HDDR particles exhibited the best homogeneous distribution of rE-rich phase. The result of transparent electron microscopy (TEM) and energy dispersive spectrometry demonstrated the nature of (Ce, Pr, Nd)-rich phase and (Ce, Pr, Nd)2Fe14B for the rE-rich phase and RE2Fe14B grain phase, respectively. Examination with high-resolution TEM revealed that the optimized tdis resulted in the largest thickness of (Ce, Pr, Nd)-rich phase at grain boundaries and the consequent maximum coercivity of HDDR particles. The orientation of the optimized HDDR particles was analyzed with X-ray diffractometer and electronback-scatter diffractometer. The result revealed well textured HDDR particles and the subordinate nanograins with preferred (001) orientation, suggesting the inherited texture of these HDDR particles from the initial (Ce, Pr, Nd)2Fe14B grains in N45 sintered magnet. This HDDR method was proved to be a prospective strategy in recycling of Ce-contained sintered magnets.

Magnetic properties of Sm(Fe,Ti)10 alloys and their nitrides

Sm-Fe alloys with compositions of SmFe10 and SmFe9.5Ti0.5 were prepared by rapid solidification processing. The as-quenched and annealed specimens did not show sufficiently high coercivity for use as permanent magnets, but the coercivity was improved by subsequent nitrogenation of the specimens. The specimens exhibited the maximum coercivity when nitrogenated at 743 K for 20 h in this study. The optimally nitrogenated SmFe10 specimen consisted of the TbCu7-type and α-Fe phases and showed a coercivity of 10.1 kOe, whereas the optimally nitrogenated SmFe9.5Ti0.5 specimen consisted of the Th2Zn17-type phase without the α-Fe phase and exhibited a high coercivity of 17.0 kOe.

Magnetic, Electrical, and Physical Properties Evolution in Fe3O4 Nanofiller Reinforced Aluminium Matrix Composite Produced by Powder Metallurgy Method.

An investigation into the addition of different weight percentages of Fe3O4 nanoparticles to find the optimum wt.% and its effect on the microstructure, thermal, magnetic, and electrical properties of aluminum matrix composite was conducted using the powder metallurgy method. The purpose of this research was to develop magnetic properties in aluminum. Based on the obtained results, the value of density, hardness, and saturation magnetization (Ms) from 2.33 g/cm3, 43 HV and 2.49 emu/g for Al-10 Fe3O4 reached a maximum value of 3.29 g/cm3, 47 HV and 13.06 emu/g for the Al-35 Fe3O4 which showed an improvement of 41.2%, 9.3%, and 424.5%, respectively. The maximum and minimum coercivity (Hc) was 231.87 G for Al-10 Fe3O4 and 142.34 G for Al-35 Fe3O4. Moreover, the thermal conductivity and electrical resistivity at a high weight percentage (35wt.%) were 159 w/mK, 9.9 × 10−4 Ω·m, and the highest compressive strength was 133 Mpa.

Effects of processing parameters and heat treatment on the microstructure and magnetic properties of the in-situ synthesized Fe-Ni permalloy produced using direct energy deposition

The present work investigated the correlations between heat treatment and the microstructure and magnetic properties of the in situ alloyed Fe-50%Ni samples manufactured using laser-based direct energy deposition under different production conditions. The samples with high relative density were directly synthesized from the pure Fe and Ni elemental powders. In addition, a fine FCC microstructure with relatively elongated grains in the building direction was observed in the as-print samples. After applying short-time heat treatment, the grain morphology remained unchanged, while the grain size and microhardness were slightly increased and decreased, respectively. This also caused the reduction in internal residual stresses and, subsequently, partial stress relaxation in the microstructure. According to the electron probe microanalysis results, the simultaneous Fe and Ni depletion/enrichment formed during the in-situ alloying was practically decreased after applying short time heat-treatment, resulting in the significant improvement of magnetic properties, as compared to the as-built ones. The maximum magnetization, coercivity, and curie temperature of ~170 emg/g, 1.8 Oe, and 530 °C, respectively, were obtained in the optimum processed sample, which were significantly higher than those of other soft magnetic permalloys produced by additive manufacturing methods.

Effect of carbonaceous reinforcements on anticorrosive and magnetic properties of Ni-Cu based composite coatings prepared by pulsed electrodeposition

Magnetic and anticorrosive properties of Ni-Cu alloy-based composite coatings prepared by pulsed electrodeposition reinforced with CNT (Ni-Cu-CNT), graphene (Ni-Cu-G), and diamond (Ni-Cu-D) have been assessed in the current work. The corrosion behavior of the composite coatings was evaluated in a 3.5% NaCl corrosive medium. Linear polarization test performed within ±10 mV with respect to open circuit potential (OCP) unveiled that graphene added coatings exhibited maximum polarization resistance (~13.1 kΩcm2) followed by the Ni-Cu-D (~9.1 kΩcm2), the Ni-Cu-CNT (~8.3 kΩcm2), and the Ni-Cu with a minimum resistance of ~4.2 kΩcm2. Electrochemical impedance spectroscopy tests performed with a signal perturbation of ±10 mV with respect to OCP and frequency sweep from 105 Hz to 10−2 Hz elicited maximum film resistance of ~32 kΩ cm2 for the Ni-Cu-G coating, which could be attributed to the high area to volume ratio, α ~134/m, of graphene nanoflakes inducing strong particle-matrix interaction and to the formation of micro galvanic cell between the graphene particles and the Ni-Cu matrix where the surface was covered predominantly with graphene, eventually lowering the corrosion rate to 5.91 MPY. For Ni-Cu-D coating, the uniform dispersion of diamond particles prohibits localized corrosion. In contrast, agglomeration of CNTs in Ni-Cu-CNT causes ~50% reduction in corrosion resistance compared to diamond reinforced coating. However, corrosion resistance of CNT grafted coating was around 2.5 times higher than Ni-Cu (~4.2 kΩcm2), which can be imputed to the filling of the pores, cracks, and crevices by CNT fibers. The hysteresis loops of Ni-Cu composite coatings traced by a vibrating sample magnetometer indicated that CNT incorporation enhanced the magnetic saturation to ~1.89 Am2/kg from ~0.84 Am2/kg (Ni-Cu) and maximum coercivity of ~110 Oe (~78.91 Oe for Ni-Cu). However, graphene and diamond addition has negligible effect on the magnetic properties of the coated systems. The enhanced anticorrosive and magnetic properties of proposed coating designs consisting of Ni-Cu matrix with carbonaceous reinforcements impart multifunctionality to the system. The marine industry can successfully adopt the proposed coating systems to protect propellers shafts, ship hulls, and specialty sensors.

Magnetic Properties of Tetragonal SmFe12−xMox Alloys in Bulk and Melt‐Spun Ribbons

Currently, electric motors and generators use high‐energy permanent magnets based on RE2Fe14B phases (RE: rare earth) with high amounts of RE often including heavy‐RE metals (Dy, Tb), the most critical group of the raw materials. REFe12 alloys are seen as potential alternatives to RE2Fe14B because they contain a significantly lower amount of RE metals with similar or better values of remanent magnetization (MR) and high magnetocrystalline anisotropy, which can give rise to a large energy product (BH)max. Herein, the effect of heat treatments on the coercivity and magnetic properties on melt‐spun ribbons of SmFe12−xMox (x = 0.5, 1) alloys with wheel speeds of 15 and 35 m s−1 is studied. The maximum coercivity after heat treatments is obtained in as‐spun ribbons at a speed of 35 m s−1. For the x = 0.5 ribbons, μ0Hc increases from 0.06 to 0.36 T, while for the x = 1.0 ones μ0Hc is enhanced from 0.02 to 0.34 T. The highest values of saturation magnetization are obtained for the x = 0.5 ribbons (≈145 Am2 kg−1).

Enhancement of magnetic properties and microstructural changes in TbCu7-type Sm-Fe-Co-Nb-B melt-spun ribbons

The effects of annealing conditions on magnetic properties, phase, and microstructural changes in Sm-Fe-Co-Nb-B melt-spun ribbons were investigated, and the dependence of magnetic properties on Sm and B composition was also investigated. SmxFe80.9−(x+y)Co16.4Nb2.7By amorphous ribbons were prepared by melt-spinning and then annealing. After annealing at 625 °C, the Sm6.2Fe66.4Co16.4Nb2.7B8.3 ribbons exhibited crystallization of hard-magnetic TbCu7-type phase, and the coercivity increased as the annealing time was increased to 9 h. The grain size of the TbCu7-type phase as estimated from transmission electron microscopy (TEM) images was 20–50 nm for ribbons annealed for 9 h. Three-dimensional atom probe (3DAP) analysis revealed that Nb and B became enriched at grain boundaries and tended to condense at the grain boundaries with increasing annealing time. Non-magnetic Nb and B enrichment at the grain boundaries in fine TbCu7-type grains thus promotes magnetic decoupling between TbCu7-type phases and suppresses domain wall propagation, resulting in high coercivity. Composition dependence on magnetic properties was investigated. Optimum annealing time tended to increase with increasing Sm content. The Sm6.7Fe65.9Co16.4Nb2.7B8.3 ribbons exhibited a maximum coercivity of 695 kA⋅m−1 by annealing at 625 °C for 21 h and subsequent slow cooling at a cooling rate of 4 °C⋅h−1. As B content decreased, coercivity decreased and remanence increased. The Sm6.2Fe68.7Co16.4Nb2.7B6.0 ribbons exhibited a high σr of 100 A⋅m2⋅kg−1 and moderate HcJ of 540 kA⋅m−1 after optimal annealing. An isotropic bonded magnet was fabricated from this ribbon. The bonded magnet exhibited high magnetic properties of Br = 0.82 T, HcJ = 538 kA⋅m−1, and (BH)max = 98 kJ⋅m−3, and small temperature coefficients of α(Br) = −0.06%⋅°C−1 and β(HcJ) = −0.27%⋅°C−1.

Optimization, structural, optical and magnetic properties of TiO2/CoFe2O4 nanocomposites

Magneto-optical TiO2/xCoFe2O4 nanocomposites having various concentrations of CoFe2O4 (x = 2, 4 and 6 wt %) were prepared using facile mechanical mixing. X-ray diffraction was employed for the phase examination and microstructure parameters. X-ray diffraction spectra proved the formation of two separate phases: tetragonal titanium dioxide (TiO2) and face-centered cubic cobalt iron oxide. The structure was further verified by recognizing the selected area electron diffraction (SAED) pattern recorded by a high-resolution transmission microscope. The optical investigation of the prepared nanocomposites verified that the optical band gap values varied from 3.1 eV for pure TiO2 to 3.05 eV for TiO2/CoFe2O4 (6 wt %). The refractive index, optical dielectric constant and loss factor were discussed in detail. The nanocomposites (TiO2/xCoFe2O4) demonstrated ferromagnetic characteristics and their magnetic parameters were affected by the CoFe2O4 percentage in the composites. The sample x = 2 wt % depicted the maximum magnetic exchange bias at room temperature. Moreover, it showed maximum coercivity (HC) and magnetic squareness ratio (SQ), which makes it suitable for spintronic applications.

Structural, dielectric and magnetic properties of Nickel-Chromium substituted Magnesium ferrites, Mg1–Ni Fe2-xCrxO4 (0 ≤ x ≤ 0.7)

In this paper, we report the structural, dielectric, and magnetic properties of Mg1–xNixFe2-xCrxO4 (0 ≤ x ≤ 0.7) ferrites synthesized via a solid-state process. The XRD patterns indicated forming a single-phase cubic spinel structure with a Fd-3 m space group for all samples with crystallite sizes ranging from 31.63 to 73.52 nm. Scanning Electron Microscopy (SEM) showed the formation of dense microstructure with an average grain size of 129.2 to 414 nm. The elemental analysis (EDS) confirmed the chemical purity for all the prepared samples. The saturation magnetization (Ms) was found to be maximum for the composition x=0.3, after which it decreased due to the lower magnetic moment of Cr3+ ion (3 μB) than that of Fe3+ ion (5 μB). The samples' maximum magnetic saturation and coercivity are 62.04 emus/gm and 6.8 KOe, respectively. The measured sample's dielectric constant (ε') and loss tangent (tan δ) decreased with the increased applied field frequency, showing normal behavior. This can be explained in light of Maxwell–Wagner interfacial polarization and hopping of electrons between the Fe2+ ↔ Fe3+ ions. Thus, the synthesized Ni-Cr substituted MgFe2O4 ferrite material is promising for recording materials.

Micrometer thick Sm-Co films for applications on flexible systems

In the industry 4.0 eco-system, flexible electronic devices bear a huge potential for a broad range of applications due to their diverse properties, such as high stretchability, biocompatibility, portability, light weight, and low costs. In this work, Cobalt-Samarium permanent magnetic thin films on flexible polyimide substrate are studied. The influence of the sputter deposition pressure on the structural, morphological, and magnetic properties is analyzed. A method for growing flexible magnetic films is proposed by achieving a maximum coercivity of 13.86 kOe and an energy product of 16.9 MGOe. These results lay the foundations for the design and fabrication of flexible magnetic devices.

A high throughput study of both compositionally graded and homogeneous Fe–Pt thin films

Compositionally graded Fe–Pt thin films were prepared on stationary 100 mm Si substrates by magnetron sputtering a base target of Fe on which a piece of Pt is asymmetrically positioned. Energy dispersive X-ray analysis was used to map the variation in film composition across the substrate, as a function of the size of the Pt piece. A scanning polar Magneto-Optical-Kerr-Effect system was used to probe the influence of composition and post-deposition annealing conditions (temperature and time) on coercivity. In this way, the maximum coercivity achievable for the sputtering system used could be established in a high throughput fashion. The evolution in coercivity with composition was correlated with the formation of L10 FePt and changes in its lattice parameters, as determined by scanning X-ray diffraction. High throughput coercivity mapping was then carried out on homogeneous Fe–Pt thin films of different compositions treated to different annealing conditions. This study serves as a step towards the integration of coercive FePt films into collectively fabricated devices.