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Magnetic encoders are composed of a magnetic sensor, a hard magnetic recording medium and a signal processing circuit. Electrodeposited micro-magnet arrays produced by micro-fabrication are promising recording media for enhancing encoder performance. However, two major engineering issues have yet to be resolved. One issue is an unknown relationship between the feature sizes of micro-magnet arrays and their stray field shapes, and another issue is the formation of micro-cracks due to the built-up residual stresses of thick films. In this study, we investigated the effect of feature sizes on the emanating stray field shape at various observation heights. Feature sizes include two height (i.e., film thickness) values of 78 μm and 176 μm, and both width and spacing with three values of 360 μm, 520 μm and 680 μm. Ultrasound-assisted agitation was adopted for investigating the effects of electrodepositing current densities on the film crystalline microstructures and magnetic properties. Narrowing the width of micro-magnets helps the stray field to become a sinusoidal profile. Thinner film, i.e., thickness 78 μm in this study, supports the stray field taking on a sinusoidal profile. Moreover, the spacing between the micro-magnets plays a key factor in determining the shape of the stray field. Under 37 kHz/156 W ultrasound agitation, the optimal hard magnetic properties of electrodeposited CoMnP films are residual magnetization 2329 G and coercivity 968 Oe by a current density of 10.0 mA/cm2. Ultrasound-assisted electrodeposition, along with duly designed feature size, facilitates the micro-magnet arrays having a sinusoidal stray field shape using high quality films. Furthermore, for the first time, a systematic understanding of feature-size-dependent stray field evolution and improved polarities quality has been realized for the recording media of sinusoidal magnetic encoders. [ABSTRACT FROM AUTHOR]

The density functional theory (DFT) framework in the generalized gradient approximation (GGA) was employed to study the mechanical, dynamical, and thermodynamic properties of the ordered bimetallic Fe-Pt alloys with stoichiometric structures Fe3Pt, FePt, and FePt3. These alloys exhibit remarkable magnetic properties, high coercivity, excellent chemical stability, high magnetization, and corrosion resistance, making them potential candidates for application in high-density magnetic storage devices, magnetic recording media, and spintronic devices. The calculations of elastic constants showed that all the considered Fe-Pt alloys satisfy the Born necessary conditions for mechanical stability. Calculations on macroscopic elastic moduli showed that Fe-Pt alloys are ductile and characterized by greater resistance to deformation and volume change under external shearing forces. Furthermore, Fe-Pt alloys exhibit significant anisotropy due to variations in elastic constants and deviation of the universal anisotropy index value from zero. The equiatomic FePt showed dynamical stability, while the others showed softening of soft modes along high symmetry lines in the Brillouin zone. Moreover, from the phonon densities of states, we observed that Fe atomic vibrations are dominant at higher frequencies in Fe-rich compositions, while Pt vibrations are prevalent in Pt-rich. [ABSTRACT FROM AUTHOR]

In the recent decade, advancements in technology and the excessive use of electronic devices in everyday life have harmed human health and produced electromagnetic pollution. To overcome these problems, hexagonal ferrites are used as excellent microwave-absorbing materials to clean the environment and protect human health. In this study, chromium (Cr3+) substituted Y-type BaSrCo 2 Cr x Fe 12-x O 22 hexaferrites (x = 0.0, 0.5, 1.0, 1.5, and 2.0) have been synthesized through self-ignited sol-gel method and sintered at 1150 °C for 5.5 h. The single phase of the synthesized nanomagnetic materials was confirmed by X-ray diffraction analysis. FTIR analysis unfold the Fe–O vibrational bands at tetrahedral and octahedral sites due to iron oxide base material. The incorporation of Cr3+ limits the transfer of electrons. As a result, DC electrical resistivity significantly increases from 7.59 × 109–4.85 × 1010 (Ω cm). The dielectric behavior and impedance analysis was carried out in the 1 MHz - 6 GHz range. By replacing Cr3+, the dielectric constant and loss exhibit a decreasing behavior. For all compositions, the values of reflection loss are calculated in the range of −39.37 to −32.95 to make them excellent microwave-absorbing materials due to their lower cost, small size, and lightweight properties. The substitution of Cr3+ increases the saturation magnetization (61.35–96.10 emu/g), coercivity (62.31–897.99 Oe), and remanence (12.30–46.52 emu/g). An increase in the coercivity value indicated that samples are thermally stable and suitable for perpendicular magnetic recording media. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles have been intensively investigated owing to their huge potential as diagnostic, therapeutic, and drug-carrier agents in biomedicine, sorbents in environmental technologies, sensors of various inorganic and organic/biological substances, energy-generating and storing materials, and in assorted biotechnological and industrial processes involving microbiology, pigment industry, recording and magnetic media or (bio)catalysis. An eminent interest in exploring the realm of iron oxides is driven by their chemical and structural diversity, high abundance, low cost, non-toxicity, and broad portfolio of chemical procedures enabling their syntheses with desirable physicochemical features. The current review article centers its attention on the contemporary advancements in the field of catalysis and environmental technologies employing iron oxides in various chemical forms (e.g., hematite, magnetite, maghemite), sizes (∼10–100 nm), morphology characteristics (e.g., globular, needle-like), and nano architecture (e.g., nanoparticles, nanocomposites, core–shell structures). In particular, the catalytic applications of iron oxides and their hybrids are emphasized regarding their efficiency and selectivity in the coupling, oxidation, reduction, alkylation reactions, and Fischer–Tropsch synthesis. The deployment of iron oxides and their nanocomposites in environmental and water treatment technologies is also deliberated with their roles as nanosorbents for heavy metals and organic pollutants, photocatalysts, and heterogeneous catalysts (e.g., hydrogen peroxide decomposition) for oxidative treatment of various contaminants. The associated challenges and potential progress in iron-oxide-based catalytic and environmental technologies are highlighted as well. Young chemists, researchers, and scientists could find this review useful in enhancing the usefulness of nano iron oxides in their investigations and developing sustainable methodologies. [ABSTRACT FROM AUTHOR]

Co-precipitation method was used to fabricate Zr-Al substituted M-Type barium hexagonal ferrite with a unique composition Ba1-xZr0.5x Al0.3 Fe11.7 O19 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5). The materials were characterized using Fourier Transform Infrared spectroscopy and a magnetic hysteresis loop. For each sample, the values of Ms, Hc, Mr, remanence ratios (Mr/Ms), and magneton number (nB) are determined using M-H loops. The Mr/Ms ratio of the synthesized hexaferrites particles is between 0.001017 and 0.143103, indicating a single magnetic domain. FTIR spectroscopy was used to study the inter-atomic forces and gives information about the absorption and emission spectrum for solids, liquids and gases. The results indicate that the synthesized compounds may have potential use as perpendicular magnetic recording media due to the growing trend in saturation magnetization, remanence, and coercivity. [ABSTRACT FROM AUTHOR]

Thin ferromagnet/heavy metal multilayer films are considered as prospective media for a magnetic recording and Co/Pd films are a good example of such materials. In this work, the magnetic properties and micromagnetic structure of Co/Pd multilayer films are studied with different bilayer thicknesses ([Co(0.3 × t nm)/Pd(0.5 × t nm)]10), but with the same ratio Co versus Pd. Transmission electron microscope and X‐ray diffraction studies allow authors to suppose that the investigated films are highly mixed alloys. Magnetic force microscopy and Lorentz transmission electron microscopy showed the presence of various micromagnetic features in the films. Along with skyrmions that are well‐known magnetic topological artifacts some new features are revealed, which are interpreted as 360° domain walls, skyrmioniums and the combination of the above two. It is found that the type and density of micromagnetic features strongly depend on the bilayer thickness parameter (t). The effect is associated with the peculiarities of interfacial magnetic interactions in the samples with highly mixed interfaces. The tooling coefficient represents a useful tool of the electron beam evaporation technique enabling wide manipulation of micromagnetic particles, in particular, skyrmioniums that are currently considered a prospective media for current driven magnetic recording. [ABSTRACT FROM AUTHOR]

The use of reverse micelles as nanoscale hydrophilic voids of microemulsions in the manufacture of ferrites has been recognized since the 1960s, but there has been very little attention on the structural and magnetic properties with respect to surfactant concentration. This paper investigates the influence of surfactant sodium dodecyl sulphate (SDS) concentrations on cobalt ferrite (CoFe2O4) nanoparticles prepared by reverse micelles at annealing temperatures 250°C and 500°C. Samples with varied cobalt to SDS ratios (Co: SDS = 1: 0.33, 1: 0.5, 1: 0.66) were subjected to XRD, TGA, TEM, FTIR and VSM Studies. All the samples exhibited single-phase spinel structures with crystalline diameters ranging from 10 to 18 nm. As the SDS concentration increased the crystallite size decreased. The TEM images showed the particle size in the range of 7.6 -17.7 nm. VSM investigations show the ferromagnetic behavior of the sample. The observed increase in coercivity with respect to annealing temperature for the same concentration reflects the single-domain nature of the nano particles. This underscores the crucial role of annealing conditions in customizing cobalt ferrite nanoparticles as a suitable application in longitudinal magnetic recording media. [ABSTRACT FROM AUTHOR]

Embedded Mask Patterning (EMP) has been proposed as a cost-effective fabrication method to be capable of patterning sub-5-nm grain sizes for highly ordered L10-FePt media for Heat-Assisted Magnetic Recording (HAMR). Understanding the etching mechanism of FePt is critical to maintaining the highly ordered L10 structure and low damage to magnetic grains. In this research, a reactive Molecular Dynamics (MD) model is developed to study methanol (MeOH) plasma etching on highly ordered continuous L10-FePt media film. The model describes the reactive interaction mechanism between the plasma products CO/H2 molecules and Fe/Pt atoms. It shows the dominant Fe-C interaction upon the dissociation of CO ligands leads to formation of large and volatile Fen-C clusters contributing to high chemical etch yield. [ABSTRACT FROM AUTHOR]

The effects of composition, temperature, and frequency-dependent dielectric properties of barium-nickel-based ferrites have been investigated. The conventional ceramic technique prepared the compositions BaNi2-xZnxFe16O27 (at x = 0.0, 0.4, 1.2, and 2). The analysis of X-ray diffraction patterns showed that they were single-phase. The average grain size, lattice constant, and density were found to increase as Zn2+ ion substitution increased. According to the frequency and Zn concentration, the dielectric parameters were properly set. Overall, the dielectric properties of this sample make them a suitable candidate for flexible supercapacitors and are best suited for high-frequency region applications. The initial magnetic permeability of the prepared sample was increasing as the Zn ion contents increases. The produced samples were suitable for application as microwave absorbers, data storage appliances, and magnetic recording mediums. [ABSTRACT FROM AUTHOR]

Nickel doped magnesium-manganese spinel ferrites with nominal composition Mg0.5Mn0.5Fe2-xNixO4 (x ​= ​0.0, 0.15, 0.20, 0.25) nanoparticles are synthesized using WOWS sol gel method. Initially, the mixture is heated along with continuous stirring to dissolve all precursors and then, precursors' mixture is converted it into gel, and finally a fluffy powder is obtained. Powder and some prepared pellets of all samples are annealed at 700 ​°C in a furnace for 1 ​h. The x-ray diffraction (XRD) spectra revealed that all samples are of single-phase spinal crystal structure and possess a good crystallinity. The crystallite size obtained from XRD data decreases with the increase in doping concentration. The lattice parameter has values from 8.35 to 8.38 ​Å. Surface morphology observed by scanning electron micrographs (SEM) reveals that most of the particles are of almost spherical shape and size distribution of the particles varies in the range of 71–84 ​nm. Dielectric constant and dissipation factor decreases sharply at low frequencies and becomes almost constant at higher frequencies. Dielectric constant and dissipation factor decreases from 8.82 to 1 and 0.18 to 0.01 respectively with the increase in doping concentration. Results obtained from vibrating sample magnetometer (VSM), reveals the increasing trend in both saturation magnetization and coercivity with the increase in nickel concentration. The synthesized material could find its application data storing cards and magnetic recording media. [ABSTRACT FROM AUTHOR]

To apply Nd–Fe–B thin films for mass-produced heat-assisted magnetic recording media, we investigated the high-rate sputtering conditions required to obtain c-axis textured Nd2Fe14B thin films and analyzed the growth mechanism. Magnetization curves indicated that higher substrate temperatures and sputtering rates resulted in a higher degree of perpendicular magnetic anisotropy; a Nd–Fe–B layer deposited at a substrate temperature (Tsub_0) of 600 °C and a sputtering rate (Rsp) of 2.6 nm/s had the easy axis perpendicular to the film plane. The dependence of the magnetic properties on the sputtering rate was due to a decrease in the substrate temperature during sputtering; there was a threshold for obtaining a high squareness ratio. X-ray diffraction analysis and transmission electron microscopy (TEM) images showed that the c-axis textured Nd2Fe14B crystal phase was formed in the Nd–Fe–B layer deposited at Tsub_0 = 600 °C and Rsp = 2.6 nm/s, which resulted in the highly perpendicular magnetic anisotropy. In addition, the TEM images showed a layer of Nd2Fe14B with no obvious lattice fringes near the interface between the Nd–Fe–B layer and Mo underlayer, while the lattice fringes of the Nd2Fe14B phase were not parallel to this interface but gently curved along the Mo cap layer. We propose that the c-axis orientation was achieved by the rotation of the c plane, which has the lowest surface energy in the Nd2Fe14B phase, toward the vacuum-side surface during sputtering. [ABSTRACT FROM AUTHOR]

The Monte Carlo simulations were used to investigate the ground-state phase diagrams of Ising nanowires for core–shell structure with mixed spins 3/2 and 2. The magnetic phase diagrams obtained found and are dependent of crystal and magnetic fields. Magnetic phase diagrams are dependent of exchange interactions for n-polygon at the surface shell and are dependent also of crystal field. The exchange interaction dependences of magnetization and the transition temperature are calculated by Monte Carlo simulation. The changes of magnetization depending on the crystal field and n-polygon increasing. The phase transition from ordered phase to disordered phase is found. The transitions temperatures are found of each polygon. The magnetic coercive fields, saturations and remanent magnetizations have been deduced for different magnetic parameters. The surface of hysteresis cycle is dependent of the effect of n-polygon, temperature, and exchange interactions. This magnetic behavior offers new perspectives for applications in advanced technologies including spintronics, logic devices and novel magnetic recording media, functionalization and bioengineering and sensor devises. [ABSTRACT FROM AUTHOR]

The effect of the location of an additional Au layer (top, intermediate, and bottom) on the residual stresses, structure, the transformation of the disordered A1 phase into the ordered L10 FePt phase, and magnetic properties of layered FePt(15 nm)-Au films on SiO2(100 nm)/Si(001) substrate is investigated. The ordering processes in the films separated from the substrates during in situ annealing are studied as well. It is shown that the level of mechanical stresses depends on the Au layer location and the number of interfaces in FePt–Au films. Both films (on the substrate and separated from it) with an intermediate Au layer had the lowest temperature of the beginning of L10 phase formation. During annealing, diffusion of Au and its redistribution along the grain boundaries of the L10 FePt phase occur. An increase in the Au concentration along the grain boundaries reduces the exchange interaction between them and increases the coercivity of the FePt/Au and Au/FePt films. [ABSTRACT FROM AUTHOR]

Ultradense arrays of magnetic nanoelements present considerable interest for extending areal densities in magnetic recording media, provided that they display high switching fields and corresponding low standard deviations. Here, we report the switching field distribution of bottom–up synthesized single-crystalline vertical Co nanowires self-organized in 2D hexagonal superlattices. The combined shape and Co hexagonal compact magnetocrystalline anisotropies in individual nanowires of diameter as small as 6 nm define a robust perpendicular magnetic anisotropy despite important interactions in superlattices of 10 × 1012 NWs/in2. Using quantitative analysis of temperature-dependent first-order reversal curves, we capture the switching field distribution in this dipolar-coupled perpendicularly magnetized nanomagnets. First, the interwire dipolar interactions are treated separately and show a dominant mean field character with temperature independent amplitudes that scale with the nanowire packing fraction. Then, the intrinsic switching field distribution, namely, independent of interwire interactions, is determined as a function of temperature in the 5–300 K range. The mean value and deviation are both found to be driven by the intrawire dipolar interaction and the temperature-dependent uniaxial magnetocrystalline anisotropy, but of smaller amplitudes than those expected from bulk behavior. With coercive fields ranging between 0.3 and 0.8 T, the switching field deviations relative to coercivity reach 20%, which is a moderate value regarding pitch arrays as small as 8 nm. [ABSTRACT FROM AUTHOR]

Thermal modulation of magnetism in magnetic recording media is a novel technique to increase the recording density. L10-FePt is a promising material for the media; however, experimental observation of its magnetization dynamics characterized by the Gilbert damping constant α is technically difficult because the dynamics is in the terahertz (THz) frequency range. A cutting edge technique in THz spintronics, an all-optical pump–probe method, leads us to achieve the detection of THz magnetization dynamics in nanometer-scale thin films with thermal heating. Here, thermal modulation of the magnetization dynamics for L10-FePt nanogranular and continuous films is discussed using the all-optical method. The effective damping constant for the nanogranular film decreased from 0.18 to 0.064 with increasing the temperature, and the thermal modulation decreased the extrinsic contribution, while this increased α above 530 K. This observation regarding the thermal modulation of the magnetic damping is valuable to design future high-density magnetic recording media. [ABSTRACT FROM AUTHOR]

The signal-to-noise ratio (SNR) of a bit series written with heat-assisted magnetic recording on granular media depends on a large number of different parameters. The choice of material properties is essential for the obtained switching probabilities of single grains and, therefore, for the written bits' quality in terms of SNR. Studies where the effects of different material compositions on transition jitter and the switching probability are evaluated were done, but it is not obvious, how significant those improvements will finally change the received SNR. To investigate that influence, we developed an analytical model of the switching probability phase diagram, which contains independent parameters for, inter alia, transition width, switching probability, and curvature. Different values lead to corresponding bit patterns on granular media, where a reader model detects the resulting signal, which is finally converted to a parameter dependent SNR value. For grain diameters between 4 and 8 nm, we show an increase of ∼ 10 dB for bit lengths between 4 and 12 nm, an increase of ∼ 9 dB for maximum switching probabilities between 0.64 and 1.00, a decrease of ∼ 5 dB for down-track-jitter parameters between 0 and 4 nm, a decrease of 1–3 dB for off-track-jitter parameters between 0 and 50 K, and an increase of ∼ 0.5 dB for the reduced bit curvature. Those results are furthermore compared to the theoretical formulas for the SNR. We obtain a good agreement, even though we show slight deviations. [ABSTRACT FROM AUTHOR]

The reduction of the transition curvature of written bits in heat-assisted magnetic recording is expected to play an important role for the future areal density increase of hard disk drives. Recently, a write head design with flipped write and return poles was proposed. In this design, a large spatial field gradient of the write head was the key to significantly reduce the transition curvature. In this work, we optimized the write pole of a heat-assisted magnetic recording head in order to produce large field gradients as well as large fields in the region of the heat pulse. This is done by topology optimization. The simulations are performed with dolfin-adjoint. For the maximum field gradients of 8.1 mT/nm, 8.6 mT/nm, and 11.8 mT/nm, locally resolved footprints of an FePt-like hard magnetic recording medium are computed with a coarse-grained Landau-Lifshitz-Bloch model, and the resulting transition curvature is analyzed. Additional simulations with a bilayer structure with a 50 % hard and 50 % soft magnetic material are computed. The results show, that for both recording media, the optimized head design does not lead to any significant improvements in the written track. Thus, we analyze the transition curvature for the optimized write heads theoretically with an effective recording time window model. Moreover, we check how higher field gradients influence the curvature reduction. The results show that a simple optimization of the conventional head design is not sufficient for effective curvature reduction. Instead, new head concepts will be needed to reduce the transition curvature. [ABSTRACT FROM AUTHOR]

We optimize the recording medium for heat-assisted magnetic recording by using a high/low T c bilayer structure to reduce AC and DC noise. Compared to a former work, small Gilbert damping α = 0.02 is considered for the FePt-like hard magnetic material. Atomistic simulations are performed for a cylindrical recording grain with diameter d = 5 nm and height h = 8 nm. Different soft magnetic material compositions are tested, and the amount of hard and soft magnetic material is optimized. The results show that for a soft magnetic material with α SM = 0.1 and J i j , SM = 7.72 × 10 − 21 J / link , a composition with 50 % hard and 50 % soft magnetic material leads to the best results. Additionally, we analyze how much areal density can be improved by using the optimized bilayer structure compared to the pure hard magnetic recording material. It turns out that the optimized bilayer design allows an areal density that is 1 Tb / in. 2 higher than that of the pure hard magnetic material while obtaining the same signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

A systematic investigation of the magnetic properties and nanostructure of FePt-nitride granular films with nitride of various melting points (Tm) is reported. When Tm of nitride grain boundary materials (GBMs) is varied from 1650 to 3305 °C, the saturation magnetization (Msfilm) changes from 710 to 570 emu/cm3. The Msfilm of FePt-nitride is similar to that of FePt-oxide granular films, almost varies linearly against Tm. At almost the same Tm, FePt-nitride shows a higher Msfilm of around 70 emu/cm3 compared to that of FePt-oxide granular films. According to the torque measurement result of the saturated torque coefficient with fourfold components (L4θsat), FePt-nitride shows a smaller L4θsat than that of FePt-oxide granular films, which suggests that FePt-nitride has a smaller content of the in-plane component than that of FePt-oxide granular films. This is supported by the in-plane x-ray diffraction profile measurement, where FePt-nitride has a smaller integral intensity of (001) diffraction of the L10-FePt phase than FePt-oxide granular films. With further promotion of grain separation, nitrides are more promising GBMs than oxides due to their high Msfilm and smaller content of the in-plane component. [ABSTRACT FROM AUTHOR]

In this study, the combinatorial dependence in double magnet master for energy-assisted magnetic recording was investigated by the micromagnetic framework. Four kinds of master media, which are soft single magnet (SSM), hard single magnet (HSM), soft double magnet (SDM) and hard double magnet (HDM), were compared. Comparing single magnet and double magnet master media, more adequate combination of double magnet master media was discussed. The HSM, SDM, and HDM master media can write line/space (L/S) pattern with bit length of 20 nm, while the double magnet master media can clearly print L/S patterns comparing with single magnet in case of 10 nm. For higher coercivity EAMR media, the larger printing field causes larger recording field difference by utilizing SDM master media while in case of HDM the recording field difference is almost constant even if the printing field increases. As a result, since the recording field difference of SDM becomes larger than that of HDM as the printing field strengthens, thus, SDM master media can write the servo signals onto higher coercivity EAMR media. It was concluded that it is important for the low coercivity parts of double magnet master media to have a larger saturation magnetization due to enhancement of large recording field difference. [ABSTRACT FROM AUTHOR]

Z-type hexaferrites (HF) with polycrystalline characteristics were elegantly synthesized by co-precipitation. XRD results confirmed the Z-type ferrite nanoparticles as belonging to the polycrystalline phase and with a particle size of 6 nm. The FTIR spectrum exhibits low- and high-frequency resonances, which correspond to tetrahedral and octahedral voids and a stabilized ferrite structure. Optical properties were determined by visible light absorption between 200 and 500 nm in the UV–Vis broad reflectance spectrum. FE-SEM micrograph showed spongy morphology and strongly aggregated ions. VSM exhibits ferrimagnetic magnetic properties and got higher coercivity. These special ferrite materials will undoubtedly be useful in microwave absorption, high-frequency, and magnetic recording media. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dysprosium-substituted M-type Ca-Mg hexaferrites are successfully fabricated. • XRD patterns reveals high purity and crystalline integrity of the synthesized material. • The Rietveld refinements confirms lattice expansion. • Morphology showed platelet-shaped structures with nanoclusters of particles in the synthesized materials. • Magnetic parameters showed remarkable values of Ms = 32.13 emu g−1, Mr = 20.34 emu g−1, and Hc = 1.418 kOe. In this research, dysprosium-substituted M-type Ca-Mg hexaferrites are successfully fabricated via sol–gel combustion technique, employing a nominal composition of Ca 0.5 Mg 0.5 Fe 12-x Dy x O 19 (x = 0.0, 0.04, 0.08, 0.12, and 0.15). Analysis of XRD patterns reveals exclusive peaks corresponding to the M-type hexaferrite, with no indications of additional phases, underscoring the high purity and crystalline integrity of the synthesized material. The Rietveld refinement is used to evaluate lattice parameters ' a ' and ' c ' along with the cell volume ' V ' using the distinct iron sites. Notably, a discernible upward trend in both lattice constants and cell volume emerged with the gradual introduction of dysprosium Dy+3 ion. Hexaferrite phase formation was also confirmed through the ' c/a ' ratio which lies below the critical value of 3.98. Synthesized samples shows a composite surface morphology with adherent clusters of small crystals and well-formed individual crystals. VSM analysis suggests, remarkable results, particularly at the x = 0.15 doping level, which exhibits the highest magnetic parameters, including Ms = 32.13 emu g−1, Mr = 20.34 emu g−1, and Hc = 1.418 kOe. These results suggest that the synthesized samples hold promise as suitable contenders for optimizing recording media, offering the potential for improved data storage performance. [ABSTRACT FROM AUTHOR]

Plasmonics enables unparalleled focus of optical energy well beyond the diffraction limit of light. The coupling of light with the electrons of a metal produces a surface wave known as surface plasmon. Surface plasmons exhibit unique characteristics, including strongly enhanced local fields, high sensitivity to changes in the local environment, and energy localization to extremely small volumes not restricted by the wavelength of exciting light. However, a significant fraction of optical energy of surface plasmons is dissipated as heat. A novel application of loss-enabled plasmonics is heat-assisted magnetic recording (HAMR), in which a plasmonic near-field transducer (NFT) is used to heat a sub-diffraction-limit region of the magnetic medium of the hard disk to lower its coercivity and enable the write pole of the magnetic head to write data in closely packed magnetic bits. The NFT must deliver a sufficient fraction of the incident laser power to the magnetic medium to increase the temperature of the heated magnetic bit above its Curie temperature, without causing excessive self-heating that could limit the lifetime of the plasmonic transducer. This investigation was focused on the development of an electromagnetic-thermal model of a typical HAMR head stack that can yield simulation results illustrating the effect of material optical properties of various stack layers on thermo-plasmonic performance. The hybrid analytical/numerical approach derived in this study provides an effective means of tuning the optical properties of stacking layers in HAMR devices to optimize the thermal performance and forms a general computational framework for selecting optimum optical properties for other plasmonic devices. [ABSTRACT FROM AUTHOR]

The rare earth (Yb3+) substituted W-type hexagonal ferrites with composition CaPb 2-x Yb x Fe 16 O 27 (x = 0.0, 0.5, 1.0, 1.5, 2.0) were synthesized by a facile and cost-effective sol-gel auto combustion method with post heat treatment. The synthesized hexagonal ferrites were characterized by a variety of analytical techniques, and an impedance analyzer was used to investigate the effects of Ytterbium on structural, magnetic, spectral and dielectric properties. The relationship between their impedance, structure and dielectric properties was investigated. The X-ray diffraction patterns verify the presence of single-phase W-type hexagonal ferrites. Physical properties such as D bulk (bulk density), D xrd (X-ray density), and P (porosity) of the CaPb 2-x Yb x Fe 16 O 27 W-type hexagonal ferrites were calculated. The bulk density of all the samples was decreased, and X-ray intensity was increased with the Ytterbium replacement in the W-type hexaferrite. By adding Yb3+ ions, the lattice parameters, cell volume and X-ray density were reduced due to the substitution of ytterbium with smaller ionic radii compared to the lead ion with large ionic radii. The AC-conductivity was increased from (1.523 × 10−5 to 6.699 × 10−5) Ωcm−1. The dielectric constant and tangent loss was found to decrease substantially. The magnetic properties were found to enhance by the substitution of Yb3+. The low coercivity value of Yb3+ substituted W-type hexagonal ferrites are suitable for magnetic recording media operated at a high-frequency regime. The enhancement of electrical, dielectric and magnetic characteristics suggests these materials as promising for multi-layer chip inductors (MLCIs) circuit applications. [ABSTRACT FROM AUTHOR]

L10-FePt thin film has been considered as a promising material for ultrahigh density perpendicular magnetic recording media. In this work, the L10–FePt thin films have been prepared by magnetron sputtering method on amorphous thermally oxidized SiO2 substrates and annealed by rapid thermal annealing. The texture evolution of L10–FePt thin films have been investigated according to control the film thickness. The texture was quantitatively investigated by X-ray diffraction. The interface microstructure and nano-twins were characterized by electron back scatter diffraction and transmission electron microscopy. The experimental results indicated that film thickness has a strong influence on the strength of {001} texture in L10-FePt films. When the film thickness was 5 nm, the intensity of {001} texture was the strongest. As the film thickness exceeded 15 nm, nano-twins began to appear in the growth direction of L10-FePt film, which changed the grain growth direction. Twinning will deflect the grain growth direction, which is the main reason for the decrease of {001} texture. [ABSTRACT FROM AUTHOR]

The present study focuses on the investigation of magnetic and temperature-dependent dielectric properties of Co-CuFe2O4 nanoferrites. CuFe2O4, Cu0.5Co0.5Fe2O4 and CoFe2O4 nanoparticles were prepared using sol–gel auto-combustion. X-ray diffraction (XRD) pattern shows a phase transformation from tetragonal (for CuFe2O4) to cubic (for Cu0.5Co0.5Fe2O4 and CoFe2O4) structure. Surface morphology of synthesized samples was analyzed by scanning electron microscopy, which shows formation of agglomerated, irregular shaped nanoparticles. Fourier transform infrared and Raman spectra of CuFe2O4, Cu0.5Co0.5Fe2O4 and CoFe2O4 nanoparticles support the results of XRD analysis. The UV–visible spectra of all the samples show strong absorption maxima in the visible range and are used to calculate the energy band gap of the synthesized nanoferrites. It was noticed that the value of band gap is highest for CuFe2O4 (1.58 ± 0.02 eV) nanoparticles in comparison to Cu0.5Co0.5Fe2O4 (1.18 ± 0.02 eV) and CoFe2O4 (1.01 ± 0.02 eV) ferrite systems. Magnetic study shows the highest value of coercivity (Hc) and squareness ratio (S) for Cu0.5Co0.5Fe2O4 (Hc = 959.10 ± 0.30 Oe, and S = 0.45 ± 0.05) ferrite. The dielectric measurement revealed a significantly lower value of tangent loss (tanδ) at higher frequencies for Cu0.5Co0.5Fe2O4 and CoFe2O4 ferrite samples in comparison to that for CuFe2O4. The high value of magnetic parameters, high resistivity (~ 107–108 Ω cm), and low dielectric loss at high frequencies for Cu0.5Co0.5Fe2O4 and CoFe2O4 nanoferrites suggests that the materials are potential candidate for high density magnetic recording media and also to be used in power transformers at high frequencies. [ABSTRACT FROM AUTHOR]

This work reported the first-principles calculations for the compositional dependence of the energetic, electronic, and magnetic properties of the bimetallic Fe-Pt alloys at ambient conditions. These hybrid alloys have gained substantial attention for their potential industrial applications, due to their outstanding magnetic and structural properties. They possess high magnetocrystalline anisotropy, density, and coercivity. Four Fe-Pt alloys, distinguished by compositions and space groups, were considered in this study, namely P4/mmm-FePt, I4/mmm-Fe3Pt, Pm-3m-Fe3Pt, and Pm-3m-FePt3. The calculated heats of formation energies were negative for all Fe-Pt alloys, demonstrating their stability and experimentally higher formation probability. The P4/mmm-FePt alloy had the lowest magnetic moment, leading to durable magnetic hardness, which made this alloy the most suitable for permanent efficient magnets, and magnetic recording media applications. Moreover, it possessed a relatively large magnetocrystalline anisotropy energy value of 2.966 meV between the in-plane [100] and easy axis [001], suggesting an inside the plane isotropy. [ABSTRACT FROM AUTHOR]

Shell ferromagnetism is a new functional property of certain off-stoichiometric Ni--Mn--In Heusler alloys, with a potential application in non-volatile magnetic memories and recording media. One key challenge in this field remains the determination of the structural and magnetic properties of the nanoprecipitates that are the result of an annealing-induced segregation process. Thanks to its unique mesoscopic length scale sensitivity, magnetic small-angle neutron scattering appears to be a powerful technique to disclose the microstructure of such annealing-induced nanoprecipitates. In this study, the microstructure of a zero-field-annealed off-stoichiometric Ni50Mn45In5 Heusler alloy is investigated by unpolarized magnetic small-angle neutron scattering. The neutron data analysis reveals a significant spin-misalignment scattering, which is mainly related to the formation of annealing-induced ferromagnetic nanoprecipitates in an antiferromagnetic matrix. These particles represent a source of perturbation which, due to dipolar stray fields, gives rise to canted spin moments in the surroundings of the particle--matrix interface. The presence of anticorrelations in the computed magnetic correlation function reflects the spatial perturbation of the magnetization vector around the nanoprecipitates. The magnetic field dependence of the zero crossing and the minima of the magnetic correlation function are qualitatively explained using the law of approach to ferromagnetic saturation for inhomogeneous spin states. More specifically, at remanence, the nanoprecipitates act magnetically as one superdefect with a correlation length that lies outside the experimental q range, whereas near saturation the magnetization distribution follows each individual nanoprecipitate. Analysis of the neutron data yields an estimated size of 30 nm for the spin-canted region and a value of about 75 nm for the magnetic core of the individual nanoprecipitates. [ABSTRACT FROM AUTHOR]

The dependence of double magnet master (DMM) printing characteristics on master thickness and non-magnetic separator (NMS) thickness is investigated using micromagnetic simulation. It is found that the recording field difference saturates when the master thickness reaches the bit length. The NMS, which separates the two magnetic materials of the DMM, shifts the maximum points of the recording field distribution into the softer magnet regions, decreasing the island-like non-reversed regions, thus enhancing the printing performance. The effective switching field is important for understanding magnetic printing characteristics. The printed magnetization distributions are in accordance with the switching field distribution of the recording field generated by the DMM. Therefore, optimizing the master thickness and NMS thickness effectively improves the DMM printing characteristics for various servo patterns. [ABSTRACT FROM AUTHOR]

To increase the recording density of hard disk drives (HDD), three-dimensional (3-D) magnetic recording with multiple recording layers is attracting much attention as a next-generation recording method. We have reported that the two-dimensional (2-D) partial response maximum likelihood (PRML) can achieve a good BER performance using the PR channel obtained from the differential-phase bit response in the 3-D magnetic recording system with a double recording layer. In this study, we realize the 3-D equalization by the 2-D finite impulse response (FIR) (2-D FIR) filter and 2-D PRML system over two layers and evaluate the 3-D equalization to further increase the recording density. The transfer function of the 2-D PR channels is determined by the response for the in-phase or differential-phase bits in a double-layer magnetic recording medium. The results show that the 2-D PRML channels with 3-D equalization based on the differential-phase transfer function achieve a good bit error rate (BER) performance for system noise. [ABSTRACT FROM AUTHOR]

It is assumed that heat-assisted magnetic recording is the recording technique of the future. For pure hard magnetic grains in high density media with an average diameter of 5 nm and a height of 10 nm, the switching probability is not sufficiently high for the use in bit-patterned media. Using a bilayer structure with 50% hard magnetic material with low Curie temperature and 50% soft magnetic material with high Curie temperature to obtain more than 99.2% switching probability leads to very large jitter. We propose an optimized material composition to reach a switching probability of Pswitch >99.2% and simultaneously achieve the narrow transition jitter of pure hard magnetic material. Simulations with a continuous laser spot were performed with the atomistic simulation program VAMPIRE for a single cylindrical recording grain with a diameter of 5 nm and a height of 10 nm. Different configurations of soft magnetic material and different amounts of hard and soft magnetic material were tested and discussed. Within our analysis, a composition with 20% soft magnetic and 80% hard magnetic material reaches the best results with a switching probability Pswitch >99.2%, an off-track jitter parameter σoff,80/20=0.46 nm and a down-track jitter parameter &#963down,80/20=0.49 nm. [ABSTRACT FROM AUTHOR]

The L 1 0 -FePt nanocrystals exhibit unique magnetic and catalytic properties, but suffer from the ordering difficulty. The addition of Cu can facilitate the L 1 0 -FePt ordering for some Fe–Pt–Cu alloys, however, the action mechanism is far from being well understood. In this work, a systematic study has been performed to the phase diagrams of the Fe–Pt–Cu system. The isothermal sections at 600 °C, 750 °C and 1000 °C, as well as the partial vertical sections of Fe 50 Pt 50 –Cu 50 Pt 50 and Fe 50 Pt 50 –Cu, were constructed. An emphasis has been paid to the L 1 0 -FePt phase, which has a wide composition range with a solid solubility of Cu up to 40.0 at% at 600 °C. Its order-disorder transition temperature decreases rapidly when deviating from 54 at% Pt, but at different lower rates along (FePt) 100- x Cu x and (Fe 50- x Cu x)Pt 50 with the increase of Cu. The ternary miscibility gap which originates from the Fe–Cu side has been studied by both experimental determinations and thermodynamic calculations. The results indicate that, at certain low temperatures, for instance 300 °C, the metastable miscibility gap can expand even up to 45 at% Pt, entering the L 1 0 -FePt phase region. An ordering transition mechanism of the L 1 0 -FePt phase stimulating by a two-phase separation was thus proposed. For a specially designed disordered Fe–Pt–Cu alloy, a metastable two-phase separation can take place firstly in the annealing process, driving the Cu atoms forming Cu-rich particles, leaving a large number of vacancies in the alloy, and consequently, accelerate the atomic diffusion and stimulate the subsequent L 1 0 ordering transition. These results will provide a new perspective for the composition design of Fe–Pt–Cu catalysts and magnetic recording media. [Display omitted] • Phase diagrams of the Fe–Pt–Cu system were critically determined. • Effects of Cu addition on the order-disorder transition of L 1 0 -FePt were well described. • Ternary miscibility gap of the Fe–Pt–Cu system in both stable and metastable states was established. • An ordering transition mechanism of L 1 0 -FePt phase stimulating by a two-phase separation was proposed for Fe–Pt–Cu alloys. [ABSTRACT FROM AUTHOR]

Whether the East Asian summer monsoon (EASM) migrated westward into the Asian interior during past warm periods is still unclear but is important for predicting precipitation variability in the Asian interior under future warming. Recent precipitation records from the Qaidam Basin in the Asian interior suggest that the EASM further migrated westward into the western Qaidam Basin during the middle Piacenzian warm period (mPWP: 3.264–3.025 Ma), indicating that precipitation in this ecologically fragile region was greater than it is currently. However, these precipitation records reveal weak sensitivity to insolation forcing, which is inconsistent with records from monsoon-influenced regions, hindering our understanding of orbital timescale precipitation variations in the Qaidam Basin during this Pliocene warmth. In this study, we report high-resolution (∼3 kyr) magnetic parameter-based records and medium grain size records from the GS section of the western Qaidam Basin during 3.25–2.95 Ma. We interpret magnetic parameters and grain size as precipitation proxies based on their sensitivity to precipitation variations. Our precipitation records suggest that the EASM precipitation was likely the precipitation source for the Qaidam Basin during the mPWP. At the orbital timescale, precipitation records reveal dominant 20-kyr precessional cycles, consistent with records from the Chinese Loess Plateau and the South China Sea, suggesting that the June insolation gradient controlled precipitation variations in the Qaidam Basin during the mPWP. At the 40-kyr band, precipitation records show in-phase relationships with ice sheets, and we infer that Antarctic ice sheet forcing seems to also influence Qaidam precipitation via atmospheric or marine processes. These results provide the first evidence demonstrating that Qaidam precipitation was extremely sensitive to the June insolation gradient and ice sheets during the mPWP, improving our understanding of orbital timescale precipitation variations in the Asian interior during past warm periods. • The Qaidam precipitation was dominated by the 20-kyr cycles during 3.25–2.95 Ma. • The Qaidam precipitation was also characterized by the 40-kyr cycles. • The forcing mechanism may be related to insolation and ice sheets. [ABSTRACT FROM AUTHOR]

The dielectric along with magnetic features of hexaferrites could be remarkably improved by cationic substitutions. Therefore, in the current work we synthesized cobalt substituted BaFe 11.6-x Al 0.4 Co x O 19 (0 ≤ x ≤ 1.2) hexaferrites via co-precipitation process followed by rapid sonochemical procedure. Structural analysis showed that, as the concentration of Co increased, the lattice-parameters 'a', 'c', crystallites-size, and volume increased. The SEM micrographs revealed the uniform and homogeneous distributions of particles in all samples. The two strong absorption bands indicated by FTIR analysis confirm the successful formation of M-type hexaferrites. The decreasing trend of optical band gape with cobalt doping is indicated by UV vis spectroscopy analysis. The dielectric-loss(ε ''), dissipation factor, and dielectric-constant(ε ′), increased as the content of cobalt is raised. The produced M-type hexaferrite exhibits increased AC electrical conductivity with frequency and doping concentration. Non-Debye-type relaxation is suggested by the cole–cole diagrams (Mʹ vs. Mʹʹ) for prepared samples. As Co concentrations increased, the magnetic moments per formula unit(m B) and saturation magnetization increased up to the optimal doping content of x = 0.9, after that these parameters showing decreasing trend. The magnetic anisotropy constant (K), coercivity (H c), anisotropy-parameter(B), and anisotropy-field(H a) were all showing increasing tendency with doping content. The investigations above revealed that Co replaced BaFe 11.6-x Al 0.4 Co x O 19 (0≤x ≤ 1.2) hexaferrites will be suitable for use as a permanent magnet, magnetic recording media, and other magnetic applications. Properties of BaFe 11.6-x Al 0.4 Co x O 19 Hexaferrites Prepared by Co-Precipitation process followed by Rapid Sonochemical Synthesis. [Display omitted] • Cobalt doped BaFe 11.6-x Al 0.4 O 19 samples were prepared via Co-Precipitation method followed by Sonochemical Synthesis. • The SEM analysis confirmed the homogenous distributions particles of the prepared samples. • VU-vis spectroscopy analysis indicated decrease in band gap of the prepared materials. • The dielectric properties showed an increase in dielectric constant ε ′ as cobalt concentration increased. • Saturation magnetization, coercivity and remnant magnetization showed an increasing trend with cobalt content. [ABSTRACT FROM AUTHOR]

• Noncollinear antiferromagnetic Mn 3 Sn films were epitaxially grown on MgO(1 1 1) substrates. • Spin current generated by Pt cancels out in the vertically symmetric Pt/Co multilayers. • Spin Hall angle of Mn 3 Sn obtained as 0.3945 is higher than that of conventional heavy metals. • Field-free current-induced magnetization switching was realized in Mn 3 Sn/[Pt/Co] 4 /Pt heterostructure. Spin-orbit torque (SOT) manipulation of perpendicular magnetization is essential for realizing spintronic storage and logic devices. When a charge current flows through a heavy metal/ferromagnetic layer structure, a spin current can be generated by the heavy metal and injects into the ferromagnetic layer with perpendicular magnetic anisotropy and switch its magnetization via the SOT. However, in order to realize the deterministic switching, an in-plane external magnetic field is needed to break the inversion symmetry, a technological requirement that hampers the practical application of SOT. Pt/Co multilayer is a good magnetic recording media and, thus, the all-electric manipulation of its perpendicular magnetic moments is of practical significance. The noncollinear spin structure in Mn 3 Sn allows an unconventional spin polarization direction, and the associated SOT can switch the magnetic moments in the absence of an external field. In this work, we demonstrate the field-free SOT switching of a heterostructure utilizing Mn 3 Sn and Pt/Co multilayer as the spin source and the ferromagnetic layer with perpendicular magnetization, respectively. Our results are important for advancing the development of spintronic devices based on noncollinear antiferromagnets. [ABSTRACT FROM AUTHOR]

A systematic investigation has been performed to optimize the microstructure of L10-FePt–SiOx granular thin films as recording media for heat-assisted magnetic recording. The FePt–boron nitride (BN) nucleation layer, which is stable even at 700 °C, is used to control the grain sizes and microstructure during the high-temperature processing. The study finds that films of high-aspect-ratio FePt grains with well-formed silicon oxide (SiOx) grain boundaries require the grading of the deposition temperature during film growth as well as the grading of the silicon oxide concentration. Well-isolated columnar grains of L10-FePt with an average height greater than 11 nm and diameters less than 7 nm have been achieved. Transmission electron microscopy analysis of the microstructures of samples produced under a variety of non-optimal conditions is presented to show how the microstructure of the films depends on each of the sputtering parameters. [ABSTRACT FROM AUTHOR]

Antidot lattices made of magnetic thin films are good candidates to be employed in future magnetic recording media. In this manuscript we present a study on the effect of shape and field-induced magnetic anisotropies on the magnetization reversal of 10 nm and 50 nm thick permalloy antidot lattices. Rounded antidot square lattices were fabricated using a combination of electron beam evaporation and laser interference lithography, covering surfaces of a few cm2. We demonstrate that a magnetic anisotropy induced in the samples, as a consequence of an applied magnetic field during growth, competes with the shape anisotropy that dominates the response of the patterned thin films, and that the effect of the field-induced magnetic anisotropy scales with the thickness of the antidot thin films. Finally, we have quantified the anisotropy constant attributable to the uniaxial field-induced magnetic anisotropy in our antidot lattices. These findings are supported by micromagnetic simulations performed using MuMax3. [ABSTRACT FROM AUTHOR]

This research describes the irreversibility analysis of steady flow with magnetic effects between two infinite stretching disks situated in a Darcy-Forchheimer medium. The energy equation is amended by the features of thermal radiation and heat absorption or generation. Similarity transformations are employed to transform the formulated equations into dimensionless form. Quasi linearization technique with the application of mathematical computational software MATLAB is used to acquire the numerical solution of these non-dimensional modeled equations. It is noticed that Eckert number, heat generation/absorption and Forchheimer parameter accelerate the temperature, while the radiation parameter decreases the temperature. It can also be observed that axial velocity is affected by inertia as well as porosity of the medium. Moreover, skin friction coefficient is an escalating function of porosity, magnetic and Forchheimer parameters. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The magnetic printing onto energy-assisted magnetic recording (EAMR) media by utilizing double magnet master (DMM) media has been demonstrated. The DMM media is effective for improving printing characteristics by enhancing recording field with two different magnetic patterns that consist of high coercivity and low coercivity magnets. The magnetization distributions and printing performances (PPs) for magnetic printing onto EAMR media were evaluated by the micromagnetic simulation. The DMM can clearly print the L/S and checkerboard patterns onto EAMR media, and the DMM PP was superior to that of the conventional master media. The DMM printing could write the servo-signals onto the EAMR media with the coercivity of up to 30 kOe. The narrower switching distributions of grains in EAMR media enhances the printing characteristics. The potential of magnetic printing with DMM media was revealed for writing the servo-signals onto the EAMR media. [ABSTRACT FROM AUTHOR]

In this work, we present a micromagnetic study of the performance potential of bit-patterned (BP) magnetic recording media via joint optimization of the design of the media and of the magnetic write heads. Because the design space is large and complex, we developed a novel computational framework suitable for parallel implementation on compute clusters. Our technique combines advanced global optimization algorithms and finite-element micromagnetic solvers. Targeting data bit densities of 4 Tb/in2, we optimize designs for centered, staggered, and shingled BP writing. The magnetization dynamics of the switching of the exchange-coupled composite BP islands of the media is treated micromagnetically. Our simulation framework takes into account not only the dynamics of on-track errors but also the thermally induced adjacent-track erasure. With co-optimized write heads, the results show superior performance of shingled BP magnetic recording where we identify two particular designs achieving write bit-error rates of 1.5 × 10-8 and 8.4 × 10-8, respectively. A detailed description of the key design features of these designs is provided and contrasted with centered and staggered BP designs which yielded write bit error rates of only 2.8 × 10-3 (centered design) and 1.7 × 10-2 (staggered design) even under optimized conditions. [ABSTRACT FROM AUTHOR]

In high-density magnetic recording media, magnetically isolated grains are required to increase the signal-to-noise ratio (SNR). Carbon can be used to isolate FePt grains enabling their grain size smaller than 4.3 nm. Carbon atoms segregate to the boundaries during growth and provide an exchange-breaking layer, however, some other carbon atoms remain dissolved in the magnetic alloy. To identify the upper limit of carbon concentration in $L 1_{0}$ -ordered (Fe0.5Pt0.5)100–xCx, first-principles calculations are performed based on the density functional theory (DFT). The Brillouin function and Callen–Callen empirical relation determine the temperature-dependent magnetization and magneto-crystalline anisotropy energy enabling the determination of magnetic properties and Curie temperature required by 4 Tb/in2 heat-assisted magnetic recording (HAMR) media and beyond. The calculated magnetization ($M_{s}$) of $L 1_{0}$ -ordered (Fe0.5Pt0.5)100–xCx decreases to 770 emu/cm3 at $x =20$ from 1030 emu/cm3 at $x = 0$ at 300 K, and the magnetocrystalline anisotropy constant ($K_{u}$) to 2.05 MJ/m3 at $x =20$ from 15.48 MJ/m3 at 300 K. It is striking to find that the Curie temperature ($T_{C}$) increases to 728 K at $x =20$ from 719 K at $x =0$. Regardless of carbon concentration, the magnetic anisotropy direction is the out-of-plane. Combining $M_{s}$ and $K_{u}$ at 300 K with $T_{C}$ , the $M_{s}$ – $K_{u}$ –C concentration relation is plotted to guide the design of $L 1_{0}$ -ordered Fe-Pt film for Tb/in2 recording media. It is found that the upper limit of carbon concentration is determined to be about 12 at.% to retain $M_{s} \ge800$ emu/cm3, $T_{C} \ge430$ K, and $K_{u} \ge 5$ MJ/m3, which are necessary to achieve areal densities of 4 Tb/in2 and beyond. [ABSTRACT FROM AUTHOR]

This work aims to study the structural and magnetic properties of MnxBa0.5-xCo0.5Fe2O4 nanoparticle powder ferrites (x = 0.1, 0.2, 0.3 and 0.4). The samples were synthesized via glycol-thermal method at 200 ∘ C . Single-phase formations for all as-produced samples were confirmed by XRD which revealed cubic spinel structure with space group Fd3m. The average crystallite sizes of the produced compounds ranged from 9.07 to 9.70 nm. HREM images showed that the powder particles are nearly spherical without any agglomeration. 57Fe Mössbauer spectroscopy was used to study local environments of the iron cations at tetrahedral and octahedral sites. Magnetic properties for the as-produced MnxBa0.5-xCo0.5Fe2O4 nanoferrites were investigated using a mini-cryogen free vibrating sample system at different low isothermal temperatures in external applied magnetic fields up to ± 50 kOe. The results show that the coercivity increased at lower measuring temperature due to spin freezing. The coercive fields increased from about 0.5 kOe at room temperature for all samples to 8.5 kOe, 11.5 kOe, 5.5 kOe, and 1.8 kOe at 4 K for the samples with x = 0.1 , x = 0.2 , x = 0.3 , and x = 0.4 , respectively. We also found that the saturation magnetization was affected by spin canting phenomenon. The studied nanoferrites with the obtained structural and magnetic properties could be promising candidate materials for magnetic recording media and memory devices. [ABSTRACT FROM AUTHOR]

• FePt(BN-VN, Ag, C) film shows high perpendicular magnetic anisotropy. • FePt(BN-VN, Ag, C) film illustrates high out-of-plane coercivity. • The FePt grains present a more uniform columnar structure with VN doping. • The microstructure was improved by grain boundary segregation of VN. Segregants are essential materials for forming the complexation or granular microstructure in thin films for magnetic recording media. One such film, FePt-BN, has a metallic L1 0 FePt main phase as its matrix, in addition to having BN and C segregants at the grain boundaries. Amorphous BN has sufficient mechanical strength to support the columnar growth of FePt grains, however, it has a lower deposition rate resulting in columnar grains with a nonuniform aspect ratio. Moreover, some B diffuses in the interstitial site of FePt lattices. To overcome these limitations, this study added the transition nitride VN and ZrN with equal volume percentages to replace some BN segregants in FePt(BN, Ag, C) films: substantially different segregation behaviors were observed. Microstructural imaging mapping revealed that although VN segregated the FePt grains boundary, ZrN was diffused in the lattice. The FePt-BN-ZrN film thus had more disordered grains contributing to a higher in-plane magnetization and wider hard axis magnetic hysteresis loops than did FePt-BN-VN. The FePt-BN-VN film has the highest perpendicular magnetic anisotropy constant (K u = 2.17 × 106 J/m3) and coercivity (H c = 4 T); moreover, parallel remanence magnetization was minimal with a linear in-plane magnetization loop. The FePt-BN-VN film was sputtered directly on MgO(100) but depositing the FePt-BN-ZrN film required a 2-nm-thick FePt nucleation layer. The high atomic number of Zr and high sputter yield ratio (Y N /Y metal) of ZrN may increase the sites occupied by N, potentially affecting ZrN segregation. [ABSTRACT FROM AUTHOR]

• Appearance of Raman active modes due to A 1g , E 1g and E 2g symmetry. • Collapse of the magnetic collinearity due to magnetic dilution and spin canting. • High spin state of Fe3+ ions due to occurrence of the five sexets. • Octahedrally coordinated Fe3+ ions at the 12k, 4f 2 and 2a sites. Investigations were conducted on the cation distribution and magnetic characteristics of M-type strontium hexaferrites substituted with Pr3 + and Co2+. The Raman modes that have been observed are typical modes of M-type hexaferrites in single phase. Raman modes corresponding to vibration of the entire spinel block, trigonal bi-pyramidal[2b (↑)], tetrahedral [4f 1 (↓)] as well as octahedral [12k (↑), 2a (↑), and 4f 2 (↓)] crystallographic sites as a result of A 1g , E 1g and E 2g symmetry are revealed by the analysis of the Raman spectra. The preference of Co2+ ions for the site where they replace Fe3+ was identified as the cause of the variation in the magnetic parameters. Since each sample has a squareness ratio value greater than0.5, it can be concluded that they possess a single magnetic domain structure. The Mössbauer analysis suggests that the high spin state of the Fe3+ ions is responsible for all five sexes, as indicated by the range of δ values (0.05 to 0.5 mm/s) for Fe3+. When Pr3+-Co2+ doping increases, the relative area values of the 2b site decrease, suggesting that Co2+ prefers to occupy the 2b site. The magnetic properties of the M-type hexagonal structure have been tuned as a result of the doping of Pr3+ and Co2+ cations on the structure. The produced samples have potential applications as permanent magnets and in magnetic recording media. [ABSTRACT FROM AUTHOR]