Magnetic Recording Research Articles

Characterization of Co-doped Ni-Mn spinel nanoferrites: A Multi-faceted evaluation of structural, optical, elastic, and magnetic properties

This study presents the synthesis and comprehensive evaluation of nanocrystalline CoxNi0.5-xMn0.5Fe2O4 (0.0 ≤ x ≤ 0.5) ferrites. Utilizing a variety of analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM), we characterized the structural, optical, elastic, and magnetic properties of the synthesized nanoparticles. Our findings reveal that increasing Co content leads to a systematic increase in lattice constant from 8.33 Å to 8.39 Å and influences the crystallite size, which ranges between 10 and 15 nm as determined by XRD. Notably, the band gaps of these nanoparticles span from 2.8 to 3.6 eV, varying with Co concentration. Magnetic measurements indicate a transition from superparamagnetic-like behavior at x = 0 to enhanced saturation magnetization, remanence, and coercivity with higher Co content. The novelty of this research lies in the detailed correlation between Co substitution and the resultant changes in multiple physical properties of NiMn nanoferrite, offering potential applications in various technological fields such as magnetic storage, sensors, and biomedical applications.

Mechano-thermochemical preparation of nanostructured (FeCoNiCr/Mn)3O4 high and medium entropy oxides: Structural, microstructural, magnetic and Li-ion storage characterization

Mechano-thermochemical synthesis of (FeCoNiCrMn)3O4 high-entropy oxide (HEO) and (FeCoNiCr)3O4 medium-entropy oxide (MEO), and their structural, microstructural, magnetic, surface and electrochemical characteristics are investigated. Ball milling substantially reduces crystalline sizes of oxide precursors, causing their partial solid-state dissolution, driving the rapid formation of HEO and MEO during the subsequent thermal treatment. Nanostructured HEO prepared at 900 °C (HEO-900) comprises single-phase octahedral crystals mostly within the range 60–80 nm, while MEO-900 crystals (80–120 nm) exhibit a greater degree of agglomeration. The contribution of oxygen vacancies to total surface oxygen in MEO-900 (20.6 %) is lower than that of HEO-900 (27.6 %). HEO-900 exhibits a superior reversible Li-ion storage capacity of 1050.6 mAh/g after 300 cycles at 100 mA/g, outperforming MEO-900. However, at the higher current density of 500 mA/g, MEO-900 shows superior performance, with a reversible capacity of 432.2 mAh/g (70.3 % retention) after 750 cycles. The charge transfer resistance of fresh HEO-900 (359.0 Ω) is greater than that of MEO-900 (241.4 Ω), and the average Li-ion diffusion coefficient in HEO-900 (10-13.3 cm2 s−1) is lower than that on MEO-900 at (10-13.1 cm2 s−1) due to the greater structural complexity of the former. Full cells incorporating HEO-900 and MEO-900 anodes with LiFePO4 cathode demonstrate an energy density of 296.4 and 274.6 Wh kg−1, respectively. The saturation magnetization of HEO-900 and MEO-900 is significantly high at 33.98 and 33.80 emu/g, respectively, enabling the easy magnetic recovery of electrodes made from these compounds in spent LIBs.

Magnetized Accretion onto and Feedback from Supermassive Black Holes in Elliptical Galaxies

We present 3D magnetohydrodynamic simulations of the fueling of supermassive black holes in elliptical galaxies from a turbulent cooling medium on galactic scales, taking M87* as a typical case. We find that the mass accretion rate is increased by a factor of ∼10 compared with analogous hydrodynamic simulations. The scaling of Ṁ∼r1/2 roughly holds from ∼10 pc to ∼10−3 pc (∼10 r g) with the accretion rate through the event horizon being ∼10−2 M ⊙ yr−1. The accretion flow on scales ∼0.03–3 kpc takes the form of magnetized filaments. Within ∼30 pc, the cold gas circularizes, forming a highly magnetized (β ∼ 10−3) thick disk supported by a primarily toroidal magnetic field. The cold disk is truncated and transitions to a turbulent hot accretion flow at ∼0.3 pc (103 r g). There are strong outflows toward the poles driven by the magnetic field. The outflow energy flux increases with smaller accretor size, reaching ∼3 × 1043 erg s−1 for r in = 8 r g; this corresponds to a nearly constant energy feedback efficiency of η ∼ 0.05–0.1 independent of accretor size. The feedback energy is enough to balance the total cooling of the M87/Virgo hot halo out to ∼50 kpc. The accreted magnetic flux at small radii is similar to that in magnetically arrested disk models, consistent with the formation of a powerful jet on horizon scales in M87. Our results motivate a subgrid model for accretion in lower-resolution simulations in which the hot gas accretion rate is suppressed relative to the Bondi rate by ∼(10rg/rB)1/2 .

Toroidal mode trapping in a magnetic meta-molecule

Abstract In this paper, we establish the relationship between the eigenmodes and the scattering characteristics of a meta-molecule made of magnetic disks from the point of view of the manifestation of its toroidal response. In particular, we examine the electric and magnetic dipole contributions to the scattering cross-sections obtained in the framework of the multipole decomposition method while accounting for the polarizability and magnetization induced in the structure by the field of incoming radiation. We find out that with increasing permeability, the toroidal mode is trapped in the meta-molecule due to the presence of its magnetization part, which may have a practical perspective in gyrotropy, permittivity, and permeability sensing.

Influences of Newtonian heating and Darcy's law in micropolar fluid flow over a magnetized stretchable disk: A Bayesian analysis

A laminar two-dimensional magnetized micropolar fluid flow passed through a stretchable surface is examined. The axi-symmetric time-independent thermal flow experienced the impacts of Darcy's law, thermal conductivity, and Newtonian heating. The dimensionalized flow model is governed by similarity transformations. The resulting non-linear flow system is numerically solved through Runge-Kutta-Fehlberg (RKF-45) built in scheme. The graphics illustration of velocity and thermal fields for multiple physical parameters is presented. The numerical values at the disk surface for couple stresses, thermal rate, and shear stresses are also calculated. A Bayesian approach is used to assess the association degree amongst the under-study constraints and variables. The magnitude of the microrotational profiles is enhanced by the combined effect of micropolar parameters while an opposite effect is observed in microrotational field against magnetic and porosity parameters. The temperature field is modified through enhancing values of conjugate parameters. Moreover, such thermal field is larger for variable thermal conductivity as assumed to constant fluid property.

Dual Eu3+ and Er3+ doping in ZnO nanoporous 2D frameworks for tuning photocatalytic activity, linear and non-linear optical response

Recent days, the greater attention of research materials are focusing on the porous nano frame structure due to their distinctive properties and high photocatalytic activity. The porous defective materials revealed a significant role in numerous research fields like sensors, catalysts, energy production, magnetic memory storage, bio medical etc. In our work, pure ZnO and 4f shell shielded rare earth metals doped ZnO metal oxide nanomaterials attributed in the photocatalytic dye degradation, non-linear optical and magnetic properties. We were synthesized pure ZnO and ZnO0.1–2xEuxErxHMT0.1–2x (2x = 0.025,0.05,0.075, 0.010 wt%) nanoparticles using a straightforward hydrothermal route. The hexagonal wurtzite structure of ZnO and Eu:Er-doped ZnO (Eu:Er@ZnO) exhibited by PXRD, and the optical bandgap (Eg) range from 3.14 eV to 3.18 eV was determined by Tauc relation (αhγ)2 = 0. The porous nanoplate morphology of as-synthesized materials revealed by HR-SEM and HR-TEM techniques. All synthesized materials exposed weak ferromagnetic property nature by VSM studies. Among all the synthesized materials, the 0.0025 wt% Eu:Er@ZnO nanoparticles exhibited porous nanoplate structures capable of catalyzing the breakdown of reactive black 5 (RB5) dye, achieving a photocatalytic activity of 93.2 % after 65 min of UV light exposure. The dopant concentration significantly influenced this photocatalytic activity, with lower concentrations showing enhanced performance, particularly in acidic conditions. Moreover, all synthesized porous nano-plate materials followed pseudo-first-order kinetics. Additionally, the Z-scan technique was employed to assess the nonlinear optical properties of the synthesized materials using Q-switched nanosecond Nd laser pulses at 532 nm wavelength. The open-aperture Z-scan revealed reverse saturable absorption (RSA) in all samples. The Eu:Er@ZnO porous nano-plates exhibited promising nonlinear absorption characteristics, with a higher nonlinear absorption coefficient ranging from 5.21 to 7.84 × 10−11 m/W and a lower optical limiting threshold between 0.87 and 0.95 × 1012 W/m2.

Magnetic field simulation and analysis of superconducting magnetic separator with different magnetic matrices

Superconducting magnetic separation technology leverages strong magnetic fields to separate magnetic from non-magnetic materials, vital for industries like mining, recycling, and water treatment. This study aims to elucidate the impact of various magnetic gathering media on the magnetic field distribution within superconducting magnetic separators through detailed modeling and simulation. Using Infolytica MagNet software, we simulate the magnetic field distribution of a JS-6-102 pilot-scale superconducting magnetic separator, both without media and with different magnetic matrices, such as mesh and rod media. Our results reveal that the presence of magnetic matrices significantly alters the magnetic field distribution, enhancing magnetic induction intensity and affecting field uniformity. We demonstrate that smaller mesh sizes yield more uniform magnetic fields, while larger rod diameters increase magnetic field distortion. These findings contribute to optimizing the design and efficiency of superconducting magnetic separation systems.

Investigation of magnetocapacitance and magnetoconductivity in single-phase Y-Type hexaferrite Ba2Co2Fe12O22 nanoparticles

This research paper examines the synthesis and characterization of Y-type hexaferrite Ba2Co2Fe12O22 nanoparticles produced using the sol-gel method. The study explores their structural, magnetic, and electrical properties, confirming the successful synthesis of pure-phase hexaferrites with a hexagonal structure at an annealing temperature of 1150 °C. Morphological analysis reveals changes in nanoparticle diameter based on varying annealing temperatures. The Ba2Co2Fe12O22 nanoparticles display soft ferrimagnetism, achieving a peak saturation magnetization of 52.31 emu/g at 1150 °C, along with notable magnetocrystalline anisotropy and anisotropy field. Investigations on magnetocapacitance and magnetoconductivity under magnetic fields revealed improved performance, with high magnetocapacitance (MC%) and magnetoconductivity (MσAC%) percentages of 24 % and 21 %, respectively. This suggests the potential utility of these nanoparticles in applications such as permanent magnets, magnetic recording media, and spintronic devices.

Additively manufactured FeCoNiSi0.2 alloy with excellent soft magnetic and mechanical properties through texture engineering

High-entropy alloys are widely used as structural materials and hold potential as functional materials. This study aims to develop a soft magnetic medium entropy alloy FeCoNiSi0.2 (Si0.2 MEA) with excellent soft magnetic properties and higher ductility using additive manufacturing technology. The microstructure of Si0.2 MEA is characterized by texture and large grains, with a single FCC phase structure. The texture strength of MEA initially increases and then decreases with the addition of Si, with Si0.1 MEA exhibiting the strongest fiber texture. Among the four FeCoNiSix MEAs, Si0.2 MEA demonstrates the best tensile properties (i.e. δ ∼39 %, σ0.2–287 MPA, σb∼551 MPa). The correlation generalized stacking fault energy calculation model indicates that Si0.2 MEA has the lowest generalized stacking fault energy (∼7 mJ/m2), suggesting superior ductility. The synergistic effect of texture and large grains promotes the formation of a magnetization “easy axis”, which makes Si0.2 MEA exhibit the best soft magnetic properties (Ms:150emu/g, Hc:1.04Oe). These results provide a new paradigm for developing laser additively manufactured soft magnetic medium entropy alloy.

Exploring spin polarization of heavy quarks in magnetic fields and hot medium

Exploring spin polarization of heavy quarks in magnetic fields and hot medium

Experimental study on surface optimization of dosage in magnetic coagulation process for enhancing primary treatment of urban sewage

This work aims to investigate the minimum dosage required to achieve optimal removal of carbon, nitrogen, and phosphorus in the Chemical Enhanced Primary Treatment (CEPT) process using magnetic coagulation technology. A response surface methodology was adopted to generate multiple regression models to optimize the dosages of three types of coagulation, i.e., polyaluminum chloride (PAC), polyacrylamide (PAM), and magnetic medium Fe3O4 particles (MP), based on the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), and total phosphorus (TP). The results showed that the regression models could predict results well with actual engineering results. Compared to the traditional coagulation process, the synergistic enhancement of PAC+PAM+MP in the CEPT process significantly improved the treatment effects. Based on the COD removal rates, PAC performed better than MP, followed by PAM; likewise, for the NH3-N and TP removal rates, PAC outperformed PAM, followed by MP. The optimized PAC, PAM, and MP dosages were 135.87, 1.51, and 108.36 mg/L, respectively, reaching 92.27 % COD, 71.98 % NH3-N, and 91.33 % TP removal rates with less than 5 % errors compared to the experimental verification results. These optimization models offer a practical and cost-saving reference for enhancing the primary treatment effect on carbon, nitrogen, and phosphorus removal using PAC+PAM+MP.

Microstructural, dielectric, electrical, electromagnetic, and magnetic property enhancements in GdIG /TrIG/ Mn0.2Co0.3Zn0.5Fe2O4 ferrites composites for electronic devices application

Gadolinium garnet ferrite (GdIG) and terbium garnet ferrite (TrIG), known for their favourable magnetic and dielectric characteristics, were combined with doped zinc spinel ferrite (GdIG)x-(TrIG)y/Mn0.2Co0.3Zn0.5Fe2O4(1-x-y) (at x=1 y=0, x=0 y=1, x=y=0.5, x=y=0.25, x=y=0) to achieve improved permittivity, permeability and magnetic properties with reduced magneto-dielectric losses. Our study details the synthesis process and the resulting enhancements in structural, magnetic, and dielectric properties of the prepared samples. Analysis of the X-ray diffraction (XRD) patterns confirmed the presence of a crystalline structure characterized by both cubic spinel and cubic garnet phases in the composites. The microstructures of the composites were analysed with field emission scanning electron microscopy (FESEM), revealing the variation in a grain size from 0.11 μm to 0.96 μm at x =y=0.5. A thorough link between the crystal structure and XRD spectra, transmission electron microscope (TEM), and selected area electron diffraction (SAED) patterns have all been investigated in order to enhance the characterisation of the samples. At 1KHz, the composites exhibit highest electrical resistivity values of 5.9×106 Ωm and 2.6×106 Ωm. With the incorporation of spinel ferrites in garnet ferrite composite (x=y=0.25) the highest value of dielectric constant (885.2) and low value of dielectric loss (0.07) at 100 KHz has been obtained. Permeability values, derived from permittivity data, showed an increase in real permeability values of from 1.4×1012 to 9.2×1017 for x=y=0.5 to x=y=0.25 composite. Vibrating sample magnetometer (VSM) further confirm that the composite x=y=0.25 has highest magnetic saturation (148.8 emu/g), coercivity (502 Oe) and microwave operating frequency (33.6 GHz). The observed high dielectric constant, low loss values, switching field distribution and good magnetic properties suggest the potential suitability of these samples for various electronic devices like: high frequency devices, antennas, switching devices and magnetic recording devices.

DFT study of the brownmillerite-type strontium-based oxygen-deficient perovskites SrTMO2.5 (TM = Mn, Fe, Co and Cu)

DFT studies are performed to investigate the crystal structure and geometry, electronic and magnetic properties of brownmillerite-type strontium-based oxygen-deficient perovskites [Formula: see text] (TM = Mn, Fe, Co and Cu) in orthorhombic phase. The comparison of the calculated lattice parameters shows consistency with the experiments, and all these perovskites are thermodynamically stable as revealed by cohesive energy. The spin-dependent calculations of the electronic band profiles demonstrate the metallic behavior of all these deficient perovskites. The increase in electrical resistivity and electronic thermal conductivities with temperature also confirms the metallic behavior of these compounds. The optimized ground state energies in different magnetic phases and post-DFT treatment confirm that [Formula: see text] and [Formula: see text] are stable in C-type AFM, [Formula: see text] is in G-type AFM and [Formula: see text] in A-type AFM phase, respectively. The high specific heat of these deficient perovskites makes them good candidates for high-temperature technology. Based on the above physical properties, it is expected that these deficient perovskites are potential candidates for spintronics and magnetic storage devices.

Control of chiral damping in magnetic trilayers using He+ ion irradiation

In the forefront of spintronic advancements, structures with strong perpendicular magnetic anisotropy (PMA) such as Pt/Co/Pt are essential for the miniaturization and performance enhancement of high-density magnetic storage technologies. The robust PMA characteristic of these systems facilitates the development of scalable spintronic devices, crucial for next-generation magnetic memory applications. This study investigates the interplay between PMA and the Dzyaloshinskii-Moriya interaction (DMI)—an antisymmetric exchange interaction prevalent in non-centrosymmetric magnetic systems—and its dissipative counterpart, chiral damping. While chiral damping arises from the same broken inversion symmetry as DMI, it typically introduces an additional energy dissipation channel, reducing device efficiency. Our research examines the effects of controlled helium ion (He+) irradiation on a Pt/Co/Pt system. We find that ion beam irradiation enhances interfacial intermixing, which correlates with a decrease in PMA. However, domain wall velocity measurements indicate a concurrent reduction in both DMI and chiral damping, along with enhanced velocities as irradiation fluence increases. These observations suggest that ion beam irradiation can be judiciously applied to achieve a balance between lower DMI, chiral damping, and reasonable PMA, thereby optimizing the system for improved device performance.

Evaluating the risk of data loss due to particle radiation damage in a DNA data storage system

DNA data storage is a potential alternative to magnetic tape for archival storage purposes, promising substantial gains in information density. Critical to the success of DNA as a storage media is an understanding of the role of environmental factors on the longevity of the stored information. In this paper, we evaluate the effect of exposure to ionizing particle radiation, a cause of data loss in traditional magnetic media, on the longevity of data in DNA data storage pools. We develop a mass action kinetics model to estimate the rate of damage accumulation in DNA strands due to neutron interactions with both nucleotides and residual water molecules, then utilize the model to evaluate the effect several design parameters of a typical DNA data storage scheme have on expected data longevity. Finally, we experimentally validate our model by exposing dried DNA samples to different levels of neutron irradiation and analyzing the resulting error profile. Our results show that particle radiation is not a significant contributor to data loss in DNA data storage pools under typical storage conditions.

Structure, electronic and magneto-elastic properties of rare earth nitrides Ln3NIn (Ln = Nd, Pm, Sm, Eu, Gd, Tb) anti-perovskites

Electronic structure and magneto-elastic characteristics of lanthanide nitrides Ln3NIn (Ln = Nd-Tb) are explored by DFT. The structural reported data are reliable with the experimental outcomes and the observed structural characteristics drop from Nd to Tb due to the small atomic radii of Tb compare to Nd. Electrical resistivity and electronic characteristics demonstrate that all the investigated compounds are metallic. The resistivity at 300 K emphasizes that they are effective conductors. These compounds are ideal for situation where large acting load are expected such as implants that bear a disproportionate amount of weight as endoprostheses for hip, knee and as screw, nails and plates, especially when structural materials need to have sufficient bending fatigue strength for skeletal reconstruction. These compounds are antiferromagnetic and their Neel temperatures are 18, 15, 39, 45, 27, and 33 K, respectively. These compounds might be therefore feasible for magnetic cloaking and storage technologies.

Optimization Design of the Multidimensional Heterostructure toward Lightweight, Broadband, Highly Efficient, and Flame-Retarding Electromagnetic Wave-Absorbing Composites.

A novel multidimensional electromagnetic wave-absorbing material was developed by combining carboxylated carbon nanotubes (CNT) with graphene oxide (GO) through multidimensional design, and cobalt/nickel-based metal organic frameworks (Co/Ni-MOF) were subsequently loaded onto the GO surface via its rich functional groups to form the composite absorbing material CNT-rGO-Co/Ni-MOF. Incorporating 25 wt % of CNT-rGO-Co/Ni-MOF into the paraffin matrix led to a remarkable RLmin value of -43 dB at 16.4 GHz, with an effective absorbing bandwidth (EAB) exceeding 4 GHz, all within a thickness of just 1.5 mm, showcasing its "lightweight, broadband, and high efficiency" characteristics. The exceptional electromagnetic wave absorption performance was attributed to multi-interface polarization loss, resistance loss, and magnetic medium loss. Furthermore, when incorporating 10 wt % of CNT-rGO-Co/Ni-MOF, the heat release capacity and peak heat release rate of EP/CNT-rGO-Co/Ni-MOF10 decreased by 59.2 and 52.6%, respectively.

On the impact of interlayer misalignment for dual-layer data detection in three dimensional magnetic recording

Three-dimensional magnetic recording (3DMR) is a crucial technology for significantly increasing the storage capacity of hard disk drives (HDDs). However, the presence of inter-symbol interference (ISI), intertrack interference (ITI), and interlayer interference (ILI) poses significant challenges to the accurate detection of data stored on multiple layers. This study addresses the impact of interlayer misalignment on the bit error rate (BER) performance in 3DMR systems. We evaluate the performance based on a neural network estimator for reconstructing the top-layer read response signal using feedback from a Viterbi detector. This enables the separation of bottom-layer signals by subtraction from the mixed readback signal. We introduce a dual-layer partial response maximum likelihood (PRML) detector for simultaneous bit retrieval from both layers. Furthermore, we investigate methods of a per-layer binary classifier and a dual-layer four-class classifier based on neural networks. Our study demonstrates the BER performance of these detection schemes influenced by the interlayer misalignment, especially when the offset is 0, 10%, 50%, and 90% of the bit dimensions between the two layers. The results show that the neural network-based reconstruction and separation method achieves better bottom-layer BER performance under a slight interlayer misalignment. The BER performance benefits more from a mild downtrack offset than the crosstrack offset. The neural network-based separation detection and the dual-layer PRML achieve the lowest top-layer BER and the worst bottom-layer BER when the interlayer misalignment is half a bit.

Extensive screening of novel BaXH3 (X = V, Cr, Co, Ni, Cu, and Zn) perovskites for physical properties and hydrogen storage application: A DFT study

A successful transition to a sustainable economy depends on effective hydrogen storage. To achieve this, we investigate novel inorganic transition metal-based BaXH3 (X = V, Cr, Co, Ni, Cu, Zn) perovskites using Density Functional Theory (DFT). We compute key properties such as structural, electrical, magnetic, optical, mechanical, and hydrogen storage using the GGA-PBE functional. We calculate lattice constants and unit cell volume, indicate thermochemical stability with the negative formation energy of all compounds, and confirm thermodynamic stability with phonon calculations. Investigations into the band structure and density of states (DOS) show that all compounds are metallic, with BaVH3 and BaCrH3 exhibiting magnetic characteristics. We calculate the optical properties, including refractive index, dielectric function, reflectivity, loss function, conductivity, and absorption. We verified mechanical stability using the Born stability criteria. We calculated the hydrogen storage capacities and desorption temperatures. These results indicate that the studied compounds are potential candidates for hydrogen storage in a green economy.

Simulation and experimental study of tool passivation based on magnetic elastic abrasive particles

The presence of micro-cracks and serrations on the tool often leads to its premature failure. However, these microscopic defects can be mitigated through passivation treatment of the tool. Magnetoelastic abrasive particles are new composite particles formed by using abrasive phase particles, magnetic media phase particles and polymer matrix according to a certain ratio, the abrasive particles have both viscoelasticity and magnetic conductivity. The introduction of magnetoelastic abrasive grains into the dual-disk tool passivation equipment can effectively improve the surface quality of the tool and increase the passivation efficiency. At the outset, a model for tool passivation was crafted employing the ABAQUS simulation software. This model aimed to evaluate the effects of diverse passivation variables on the stress levels, the shape of the impact, and the depth of the impact experienced by the tool. Subsequently, by applying statistical theory combined with fitting function techniques, a mathematical model was constructed to determine the passivation volume of the tool subjected to multiple magnetic elastic abrasive particles. This model was then used to examine the impact count and passivation volume associated with each passivation factor. Finally, a tool passivation experiment was conducted using a dual-disk magnetic tool passivation device. The results showed that the smaller the impact velocity of magnetic elastic abrasive particles, the stress and impact depth of the cutting tool are decreasing, and the deformation of the cutting edge is caused by compressive stress. The error of impact depth calculated by simulation and mathematical model is within 20 %, which proves that the mathematical model can better calculate the impact depth of magnetic elastic abrasive particles on the cutting edge of the tool.