Magnetic Loss Research Articles

The Effect of Sintering Temperature on the Densification and Magnetic Performance of NiCuZn-Ferrites (CuO: 0–6 wt.%)

This article reported on the effect of Cu-content and sintering temperature on the magnetic permeability and power losses of monolithic iron-deficient NiCuZn-ferrite components with low Cu-contents aimed to be used for power applications at frequencies up to 1 MHz. In particular NiαZnb1−xCuxFe1.9O4 ferrite compositions are investigated with a constant Ni/Zn atomic ratio a/b = 0.9 and 0 < x < 0.017. As found, the addition of Cu enables the achievement of good magnetic performance at lower sintering temperatures and, therefore, lower production cost. At all Cu-contents, the initial permeability as a function of the sintering temperature passes through a maximum above which structural deterioration due to asymmetric grain growth occurs. The temperature at which this maximum permeability occurs depends on the Cu content and coincides with the achievement of the maximum density of 5.1–5.2 g cm−3 (relative density ~97%). At Cu-contents x = 0.006–0.012 and sintering temperatures 1200–1100 °C power losses (tan(δ)/μ at 1 MHz, 25 °C) οf 50 × 10−6 could be achieved and initial permeabilities (10 kHz, 0.1 mT, 25 °C) of around 400 with very good frequency and temperature stability. At CuO content higher than 4 wt.% (i.e., x > 0.012) and sintering temperatures higher than 1150 °C, pronounced microstructural disturbances due to asymmetric grain growth result in low permeabilities and high losses. It is suggested that at low CuO contents and low sintering temperatures, the densification enhancement may not proceed through Cu-rich phase segregation but through the creation of oxygen vacancies.

MXene/cobalt ferrite/carbon materials based composites for efficient microwave absorption

In the present study, cobalt ferrite (CF) nanoparticles were in-situ grown on MXene/carbon-based materials (activated carbon (AC), MWCNT, and GO) to develop composites via facile hydrothermal route. The MXene/CF/MWCNTs composite (FMCNT4) achieved an excellent maximum reflection loss (RLmax) of −67.04 dB at 16.24 GHz & a thickness of 5.94 mm, whereas at the thickness of 5.86 mm, the FMCNT4 obtained a maximum effective absorption bandwidth (EAB, RL < −10 dB) of 2.73 GHz. On the other hand, replacing MWCNTs with AC in the composite (FMAC4) showed RLmax of −46.52 dB at 18 GHz and 5.1 mm thickness, it also got an EAB of 2.54 GHz at 5.5 mm thickness. The MXene/CF/GO composite (FMGO5) obtained RLmax = −17.31 @ 17.12 GHz & 6 mm. The composite having MWCNTs showed the best performance, and the reason for this remarkable MW absorption performance originated from the high impedance matching followed by dielectric polarization and magnetic losses in the composite. The formation of multiple heterointerfaces between MXene, CF, and MWCNTs enhanced the interfacial polarization, whereas the conducting MXene and MWCNTs also contributed to conduction polarization. Thus, the present investigation showcases FMCNT as an excellent synergetic nanocomposite for MW absorption applications.

The preparation and performances of Co-Zn 18H hexagonal ferrite with an ultra-high magnetic resonance frequency and low-loss characteristics

Modern 5G communication technologies require evolution of antennas towards high frequency and miniaturization. The search for magneto-dielectric materials with simultaneous high permeability, matched dielectric constant, and low loss properties for sub-6 GHz band applications has received considerable attention from both academic and industrial circles. Due to the low magnetic resonance frequency and high magnetic loss, traditional spinel and hexagonal ferrites hardly meet these requirements. In this study, polycrystalline Co-Zn 18H ferrites (Ba5Co2-xZnxTi3Fe12O31) were synthesized by co-precipitation method with only one-step sintering process. The polycrystalline Co-Zn 18H hexagonal ferrite possesses an ultra-high natural resonance frequency (14.5 GHz) and low magnetic loss (tanδμ≤0⊡10), which provides a better performance factor (PF= 68.6 GHz) at a higher operating frequency (4.97 GHz) compared to traditional microwave ferrites. The miniaturization rate of the planar inverted F antenna (PIFA) with Co-Zn 18H ferrite working at 4.0 GHz reaches 13.3 %. These results demonstrate the high potential of Co-Zn 18H ferrites for high frequency and low loss applications.

Biomimetic artificial nacre-like microfiber of Co/C modified cellulose nanofiber/Ti3C2Tx MXene with efficient microwave absorption

Although considerable efforts have been made in the fabrication of MXene-based composites for microwave absorption (MA), there is a great challenge to assemble MXene into regularly arranged microfibers prepared by wet-spinning technique for application in the field of MA due to insufficient interlayer interactions between Ti3C2Tx flakes. Heterogeneous interface design by optimizing material components to construct ingenious microstructure is crucial for efficient microwave absorbers. Herein, artificial nacre-like supramolecular microfibers of Co/C modified cellulose nanofiber/Ti3C2Tx MXene (Co/C/CNF/Ti3C2Tx) with plenty of heterogeneous interfaces were prepared by a simple wet-spinning technology through a self-assembly process induced by hydrogen bonding interactions between CNF and Ti3C2Tx. The artificial nacre-like microfibers with layered structure possess abundant heterogeneous interfaces, which facilitate multiple reflections/scattering of electromagnetic waves (EMW) between these interfaces, and at the same time promote interfacial and dipole polarization. The introduction of magnetic Co/C nanoparticles not only offer additional magnetic loss ability and improved impedance matching, but also enhance conductivity loss and polarization loss. Benefiting from these advantages, Co/C/CNF/Ti3C2Tx (1:1:1) fiber exhibits superior MA performance with a minimum reflection loss (RLmin) of up to −62.32 dB (>99.9999 % energy absorption) and a broad effective absorption bandwidth (EAB) of 5.86 GHz. The work provides a promising method for the preparation of biomimetic artificial nacre-like MXene-based microfibers with efficient MA performance, which is expected to be applied in the field of flexible wearable electromagnetic protection.

UV‐curable 3D‐printable microwave‐absorbing material with a sword‐sheath structure based on multiwalled carbon nanotube/polypyrrole nanotube/Fe3O4 composites

Multiwalled carbon nanotube (MWCNT)/polypyrrole nanotube (PPyNT)/Fe3O4 composites with a sword‐sheath structure are added to a UV‐curable resin to form a unique highly microwave‐absorbing material with a low absorbent content. Specifically tailored for high‐precision stereolithography three‐dimensional (3D) printers, the low absorbent content ensures an efficient curing and molding of the photosensitive resin. The conducting polymer polypyrrole is coated on the MWCNTs via free‐radical polymerization, forming a sheath structure. The initiator of the free‐radical polymerization, FeCl3, is converted into Fe3O4 and loaded onto the sheath structure. This ternary composite material is uniformly dispersed in the photosensitive resin with interconnected sword‐sheath structures, ensuring a favorable dielectric loss performance even at a low absorbent content. Importantly, the material exhibits both dielectric loss and magnetic loss properties. Using a UV‐cured microwave‐absorbing material with an absorbent content of 0.5 wt%, an electromagnetic loss of −22.5 dB can be achieved with a thickness of 1 mm. This UV‐cured microwave‐absorbing material facilitates the high‐precision 3D printing of microwave structures with various intricate shapes, broadening the application scope of microwave‐absorbing materials.This article is protected by copyright. All rights reserved.

Carbonyl iron/glass fiber cloth composites: Achieving multi-spectrum stealth in a wide temperature range

Multispectral camouflage in a wide temperature range is still a challenging issue owing to the incompatibility of stealth mechanisms corresponding to different spectra. Herein, we develop a flexible flaky carbonyl iron (FCI)/glass fiber (GF) cloth, using all-in-one design of microwave absorption and infrared (IR) stealth to eliminate the above contradictions. Due to micron-scale gaps and height differences on the surface of GF cloth modified with Fe3O4, FCI gains a special vertical structure, which not only induces multiple eddy centers in FCI to enhance magnetic loss but also reduces the microwave reflection area, achieving a synergistic improvement in attenuation and impedance characteristics. Therefore, FCI/GF cloth with a thickness of 2.0 mm obtains a maximum effective absorbing bandwidth of 5.82 GHz in a range of 25–400 °C. On the other hand, combination of FCI and GF cloth decreases IR emissivity while maintaining wonderful heat insulation performance, allowing objects over 250 °C to obtain promising thermal IR camouflage. The all-in-one design successfully breaks barriers faced by traditional hierarchical radar-IR compatible stealth materials such as strong reflection, great thickness, loss and impedance mismatch.

Co/C Nanocomposites with Tunable Condensed States Induced by Conformation-Mediated Strategy for Electromagnetic Wave Absorption.

The strategic regulation of condensed state structures in multicomponent nanomaterials has emerged as an effective approach for achieving controllable electromagnetic (EM) properties. Herein, a novel conformation-mediated strategy is proposed to manipulate the condensed states of Co and C, as well as their interaction. The conformation of polyvinylpyrrolidone molecules is adjusted using a gradient methanol/water ratio, whereby the coordination dynamic equilibrium effectively governs the deposition of metal-organic framework precursors. This process ultimately influences the combined impact of derived Co and C in the resulting Co/C nanocomposites post-pyrolysis. The experimental results show that the condensed state structure of Co/C nanocomposites transitions from agglomerate state → to biphasic compact state → to loose packing state. Benefiting from the tunable collaboration between interfacial polarization and defects polarization, and the appropriate electrical conductivity, the diphasic compact state of Co/C nanocomposites achieves an effective absorbing bandwidth of 7.12GHz (2.1mm) and minimum reflection loss of -32.8dB. This study highlights the significance of condensed state manipulation in comprehensively regulating the EM wave absorption characteristics of carbon-based magnetic metal nanocomposites, encompassing factors such as conductivity loss, magnetic loss, defect polarization, and interface polarization.

Construction of ZIF/CS and ZIF/CS-derivatives with high-efficiency adsorption for dyes/antibiotics and strong microwave absorption performance

Bimetallic Zn/Co-ZIF was in situ loaded onto the surface of chitosan (CS) to form ZIF/CS composites with high-efficiency adsorption of antibiotics (tetracycline (TC)) and dyes (Congo Red (CR), Malachite Green(MG)). The particle size and surface roughness of Zn/Co-ZIF can be effectively adjusted by changing the mass ratio of Zn and Co in ZIF, which helps to regulate the adsorption active sites on the surface of the composites. Meanwhile, the introduction of CS changes the pore structure of the composites, making the molecules of TC, CR and MG easily enter into the pores of ZIF/CS. When the mass ratio of Zn to Co is 1:1, the ZIF/CS composite has the optimal adsorption performance with the ultra-high adsorption capacity qm of 781.3, 1644.2 and 3243.6mgg-1 for TC, CR and MG, respectively. Impressively, the ZIF/CS-derivative (ZC3-700) from sample ZC3 after calcination at 700 °C under N2 atmosphere owns a good conductive network, which results in its superior microwave absorption performance. Herein, at 30wt% filler loading, the effective absorption bandwidth and RLmin of ZC3-700 reach 5.28GHz at 1.90mm and -68.92dB at 1.83mm, respectively. Analyses on microwave absorption mechanism point out the synergistic effect of conduction loss, dipolar polarization and interfacial polarization and magnetic loss on the attenuation of electromagnetic wave. Therefore, ZIF/CS composites and ZIF/CS-derivatives exhibit superior performance on the removal of water pollutants and the absorption of electromagnetic wave, which essentially reveals a multifunctional application of the ZIF/CS composites in the field of environmental protect.

ZIF-67 derived CoNi@carbon/RGO composites with abundant heterogeneous interfaces for electromagnetic wave absorption

The controllable structure design and composition regulation play a key role in the development of electromagnetic wave (EMW) absorbing material. Herein, CoNi@carbon/RGO absorbing materials were successfully prepared by direct pyrolysis of ZIF-67/Ni(OH)2/GO precursor. The CoNi@carbon/RGO-15 sample achieves an RLmin value of −46.14 dB and an effective absorption bandwidth (EAB) of 1.15 GHz (thickness 4.1 mm) at a low frequency with a filling amount of only 10 wt%. When the thickness is 1.5 mm, the RLmin reaches −41.09 dB and the EAB reaches 5.41 GHz, covering most of the Ku bands. After the pyrolysis, the carbon layer, Co and Ni nanoparticles, and RGO nanosheets form a three-dimensional porous structure, which builds up abundant heterogeneous interfaces and conductive networks. These factors can enhance impedance matching, dielectric, and magnetic loss. This indicates that CoNi@carbon/RGO is the potential lightweight EMW absorbing material with high performance.

Ultra-wideband electromagnetic wave absorption property with bimetallic Co6W6C/carbon

Binary dielectric materials, particularly carbide/carbon composites, have garnered considerable attention for their promising electromagnetic wave (EMW) absorption property. In this work, bimetallic carbide and carbon composite (Co6W6C/C) was successfully prepared through hydrothermal method and pyrolysis process. Characterization results reveal the growth of Co6W6C nanoparticles on two-dimensional carbon nanosheets. The mass ratio of glucose (C6H12O6) to Co6W6C was found to significantly impact the EMW absorption performance. When 150 mg C6H12O6 and 100 mg CoWO4 were added, the CWCC-2 composite exhibited an ultra-high effective absorption bandwidth of 7.49 GHz (10.51–18 GHz). In the far-domain circumstance, the highest radar cross-section acreage reached 21.24 dB m2. The exceptional EMW absorption performance can be attributed to the synergistic effects of impedance matching, electrical losses, and magnetic losses. The Co6W6C/carbon composite, synthesized through a facile approach, showcases a broad electromagnetic wave absorption bandwidth, paving the way for a breakthrough in materials science with wide-band and high-efficiency absorption capabilities.

(Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98/biocarbon composite: a broad band and highly efficient electromagnetic wave absorber

The combination of carbon and magnetic materials have drawn extensive attention for microwave absorption. In this study, high-performance microwave absorbing materials are prepared by direct mechanical mixing (Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98 (ZnNiCrFeO) with leaf biocarbon. After mixing with biocarbon, the magnetic materials present decent micro-wave reflection loss. Especially, the minimum reflection loss value of -41.08dB is achieved. The excellent conductivity of biocarbon, magnetic loss of ZnNiCrFeO, and interface polarization loss (between ZnNiCrFeO and biocarbon) jointly determined the electromagnetic absorbing performance. The appropriate impedance matching as well as the synergetic effect between the biocarbon and ZnNiCrFeO magnetic material are also considered. These achievements light the way to prepare low-cost microwave absorbents with excellent electromagnetic wave absorbing performances, utilizing the leaf as precursors.

Micro-helical Ni3Fe chain encapsulated in ultralight MXene/C aerogel to realize multi-functionality: Radar stealth, thermal insulation, fire resistance, and mechanical properties

Magnetic carbon aerogels with high porosity, ultralow density, and excellent impedance matching are considered to be a promising microwave absorption (MA) material. In this study, ethylene glycol polymerization is used to assemble Ni3Fe particles into a micro-helical chain, which is further wrapped by MXene and then encapsulated in poly-Schiff-base aerogels through the carbonyl–amine condensation reaction. Finally, ultralight TiO2/Ni3Fe/MXene/C (NFMC) aerogels are synthesized through calcination treatment. Benefiting from the electromagnetic synergistic effect of multi-dimensional and multi-component materials, the NFMC-7 aerogel exhibits excellent MA performance with a minimum reflection loss of −61.6 dB at 3.0-mm thickness and an effective absorption bandwidth of 8.16 GHz at 2.77-mm thickness under a low filler loading of 7.6 wt%. Commercial computer simulation technology is used to verify the strong magnetic and dielectric loss characteristics of Ni3Fe chains. At the same time, the NFMC-7 aerogel exhibits excellent radar stealth, heat insulation, compression resistance, and fire resistance performance, which verifies its practical applicability. Overall, this work establishes an effective strategy to fabricate multi-functional magnetic aerogels, which can serve as lightweight, thin, and strong microwave absorbers with broad absorption bandwidth.

High-performance CeFeCo/FeSiAl soft magnetic composites for megahertz power devices

Soft magnetic composites (SMCs) play a crucial role in modern electronics and electrical devices, for which challenges remain in maintaining magnetic performance and reducing loss at megahertz (MHz) frequencies. Here, CeFeCo/FeSiAl@ polyurethane (PU) SMCs have been rationally designed with the simultaneous achievement of large relative permeability, high domain-wall resonance frequency, and low power loss. As a rare-earth soft magnetic alloy, the CeFeCo is promising for high-frequency applications due to its easy-plane anisotropy, whereas FeSiAl is advantageous with increased electrical resistivity as well as approaching-zero magnetocrystalline anisotropy and magnetostriction. Hot pressing has been adopted to achieve a dense and homogeneous distribution of CeFeCo and FeSiAl powders in the PU for reduced magnetic dilution and eddy current loss. The resultant SMCs exhibit optional soft magnetic performance with large relative permeability of 21.0, low power loss of 3677.5 kW·m−3 at 5 MHz, and high domain-wall resonance frequency of 386.1 MHz. As such this work provides insights into the design of high-frequency SMCs incorporating novel rare-earth soft magnetic alloys.

Hollow carbon microsphere embedded with Fe nanoparticles for broadband microwave absorption

Nowadays, Fe-based microwave absorption materials still face crucial problems of poor oxidation resistance, lack of dielectric loss and narrow effective absorption bandwidth. In this work, we developed a feasible way of calcining and etching SiO2 microspheres coated Fe3+ and polydopamine (SiO2@Fe3+-PDA) to confine Fe nanoparticles (12 nm) in the hollow carbon microspheres with a thickness of 17 nm, which provides more interfaces and polarization sites to enhance microwave attenuation. With the increase of Fe content, the microwave absorption performance of the sample is gradually improved. When Fe content is 19.7 wt%, the sample has a minimum reflection loss (RL) of −30.9 dB and a broadband absorption bandwidth (RL ≤ −10 dB) of 11.9 GHz (6.1–18 GHz) at the thickness of 4.0 mm. The ultra-wide effective absorption bandwidth is ascribed to synergetic effect of Fe nanoparticles and carbon layer, which provide magnetic loss and dielectric loss, respectively. Moreover, the hollow structure extends the transmission path and induces the multiple scattering of the incident electromagnetic waves. The novel hollow Fe/C microspheres are promising as high-efficiency microwave absorbers with strong microwave absorption and broad absorption bandwidth.

Repeatability and reproducibility of physically consistent single sheet testing with H-coil

Measurements of magnetic losses of electric steel are usually performed by International Electrotechnical Commission standardized Epstein testers or Single Sheet Testers (SSTs). According to round robin tests, the corresponding levels of repeatability are of the order of 0.1%, and those of reproducibility are of the order of 1%. However, orders of absolute accuracy are unknown due to the applied “current method.” Here, we report corresponding tests for the so-called “physically consistent SST.” Consistency is achieved by a “giant” tangential field coil on a 50 cm long and 17 cm wide soft magnetic sample, using a thin amorphous yoke for magnetization. Tests were made in two labs with very different working conditions (sea levels of 200 and 1100 m, respectively), with very similarly built-up testers. Measurements were made for peak inductions between 1 and 1.9 T. For two distributed samples, the repeatability errors were lower than 0.3%, and the reproducibility errors were lower than 1%. This indicates that SSTs with an H-coil are not less reliable than current based ones. However, the absolute accuracy can be estimated to be much better, being close to 2%.

Electromagnetic radiation suppressor based on Co-Ti doped strontium lanthanum hexaferrite for Ku-Band applications

In this proposed work, we report Co-Ti doped Strontium-lanthanum M−type hexaferrites with general chemical formula, Sr0.85La0.15(CoTi)0.5Fe11O19 and Sr0.85La0.15(CoTi)0.75Fe10.5O19 prepared by citrate auto-combustion method. Complex permittivity, complex permeability and microwave absorptive properties of fabricated ferrite compositions were analysed in 12.4 to 18 GHz frequency range (Ku-Band). The XRD (X-ray diffraction) pattern of Co-Ti substituted compositions show single-phase M−type hexagonal ferrite indicating this co-substitution maintained the crystal phase structure. The grain diameter (average) decreased from 587 nm to 290 nm and 415 nm to 318 nm for ferrite samples with composition x = 0.50 and x = 0.75 respectively after 20 hours of ball-milling. The reflection loss (RL) exhibited the absorption bandwidth of more than 90 % (−10 dB) of value 2.41 GHz and 1.2 GHz for fabricated ferrites with chemical composition Sr0.85La0.15(CoTi)0.5Fe11O19 and Sr0.85La0.15(CoTi)0.75Fe10.5O19 respectively.. Both dielectric loss tangent and magnetic loss tangent contributed to enhance total loss tangent which represents microwave absorbing properties of the prepared ferrite samples. Reflection coefficient (S11) values for open circuit method also shows absorption bandwidth (−10 dB) of more than 90 % for these ferrites. Double layer electromagnetic absorber was simulated and observed improved reflection loss and absorption bandwidth. Therefore, these suggested ferrite samples have potential to be used as electromagnetic wave absorbing material of both single and double layer at higher frequency range.

High-efficiency electromagnetic shielding based on multipolar effect in RGO/MXene aerogels decorated with ordered Fe3O4 cluster

With the widespread use of digital systems and electronic communication devices, there is an urgent need to develop lightweight and efficient electromagnetic interference (EMI) shielding materials to address the growing problem of radiation pollution. RGO/MXene/Fe3O4 aerogels were successfully designed and synthesised using a one-step hydrothermal process induced by an external magnetic field in this study. Reduced graphene RGO, MXene nanosheets and Fe3O4 nanoparticles were suitably assembled together to achieve the combined advantages. The aerogels exhibited large specific surface area and hierarchical porosity. The material not only achieves an effective synergy between magnetic loss and dielectric loss, but also exhibits satisfactory EMI shielding performance. Magnetic field induced RGO/MXene/Fe3O4 aerogels (MIRMFE-2) exhibits the best EMI shielding performance with an average SET value of 76.9 dB. The excellent shielding performance of MIRMFE is attributed to both its 3D porous structure and the high dielectric loss due to multiple polarization relaxation, magnetic loss due to eddy current loss and natural resonance. The synthesis of MIRMFE provides an effective method for, designing high-performance and lightweight EMI shielding materials.

Facile design and permittivity regulation of porous carbon and magnetic particles based composite nanofibers towards highly efficient electromagnetic wave absorption

Two kinds of porous carbon and magnetic particles-based composite nanofibers (PCNTF-CoFe and PCNTF-NiFe) were synthesized for electromagnetic wave (EMW) absorption. Magnetic particles were used as the catalyst to increase the crystallinity of carbon and the corresponding dielectric loss ability, while porous structure was designed to improve the impedance matching. According to the results, the dielectric loss abilities of PCNTF-CoFe and PCNTF-NiFe are enhanced without significant degradation in their impedance matching condition. Therefore, through the polarization and conduction-induced dielectric loss together with the natural and exchange resonance-induced magnetic loss, the incident EMW can be attenuated rapidly inside PCNTF-CoFe and PCNTF-NiFe. PCNTF-CoFe shows a minimum reflection loss (RLmin) of −54.6 dB and effective band width (RL≤-10 dB, EABW) of 6.0 GHz at 2.0 mm, while PCNTF-NiFe shows RLmin of −33.4 dB and EABW of 5.7 GHz at 1.7 mm. Consequently, PCNTF-CoFe and PCNTF-NiFe can be promising candidates for application in EMW absorption.

Fe2AlB2@FeAl layered double hydroxides with core-shell heterostructures for electromagnetic wave absorption

The rapid development of high-performance materials has garnered considerable attention in addressing electromagnetic pollution. The construction of core-shell heterostructures is an effective approach for regulating the electromagnetic parameters of absorbers. However, these heterostructures usually lack a direct channel for charge transport between the core phase and the adhesive shell phase. Herein, Fe2AlB2@FeAl-layered double hydroxides with core-shell heterostructures were prepared using a top-down approach. The tightly connected FeAl-LDHs nanosheets to the Fe2AlB2 parent phase improved electronic transport. Compared with raw Fe2AlB2, the spherical absorber with an embroidered structure demonstrated stronger reflection loss (-15.6 dB for Fe2AlB2, −58.6 dB for Fe2AlB2@FeAl-LDHs) and a broader effective absorption bandwidth (2.2 GHz for Fe2AlB2, 3.6 GHz for Fe2AlB2@FeAl-LDHs) due to the enhanced dielectric and magnetic losses. This study presents a practical method for designing new controllable core-shell heterostructures for electromagnetic wave-absorbing materials.

Hierarchical etching-assembly engineering of Fe-based composite microspheres with balanced magnetic-dielectric synergy towards ultrahigh electromagnetic wave absorption

Hierarchical engineering of magnetic-dielectric composite microspheres has attracted increasing attention owing to its potential to enhance electromagnetic wave absorption (EMA) through magnetic-dielectric synergy. However, optimizing magnetic-dielectric balance in composite microspheres at the nanoscale remains a formidable task due to their limited component optimization and microstructural regulation. Herein, a novel approach is proposed to modify conventional carbonyl iron powder (CIP) microspheres via synergistic etching-assembly strategy. By applying a polydopamine coating, successive tannic acid (TA) etching-assembly, and pyrolysis, hierarchical iron@carbon-1/N-doped carbon (Fe@C-1/NC) composite microspheres are obtained. This overcomes the drawbacks of CIP microspheres, including their high density and poor impedance matching, which hinder EMA performance. Hierarchical carbon layer engineering can introduce abundant dipole centers, heterogeneous interfaces, and conductive networks to induce dielectric loss, while magnetic components contribute to magnetic resonance and eddy current loss, as demonstrated by the results. Accordingly, Fe@C-1/NC composite microspheres demonstrate a minimum reflection loss (RLmin) of −70.7 dB and an effective absorption bandwidth of 3.75 GHz at a matching thickness of 2.3 mm. Generally, this work paves the way towards CIP engineering to provide guidance to the future exploration of hierarchical magnetic-dielectric EMA materials.