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The easy-plane anisotropy of Y2Co17 rare earth soft magnetic alloy has high saturation magnetization, operating frequency, and good impedance matching. Therefore, it is expected to become a kind of high-performance microwave absorbing material. In this paper, Y2Co17 alloy was prepared by reduction-diffusion method, and its micro powder was prepared as polyurethane (PU) based composite absorbing materials (Y2Co17/PU composites). The microwave properties of composites with different volume fractions are calculated. The composites showed outstanding absorption characteristics in the range of 20-30 vol%, and the minimum reflection loss (RL) was less than -50 dB. When the volume fraction was 25%, the effective absorption bandwidth can cover the X-band at a thickness of 1.5 mm, and the Ku-band at a thickness of 1.08 mm. The absorption mechanism was analyzed by the interface reflection model. The RL absorption peak bandwidth mechanism was discussed by using the amplitude relation, and calculating the effective absorption bandwidth at different thicknesses. The effective absorption bandwidth values were in good agreement with the theoretical expectation.

Intermetallic complexes of rare-earth and 3d transition metals with core-shell structures are commonly employed as microwave absorbing materials due to their high saturation magnetizations and natural resonance in GHz. Hence, we synthesized Y2Co17 alloy via the co-precipitation reduction-diffusion technique, then coated the Y2Co17 magnetic powders with SiO2 to create Y2Co17@SiO2 core-shell structures. The formation of Y2Co17@SiO2/polyurethane (PU) at various volume fractions and their magnetic, electromagnetic properties were investigated using x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and vector network analyzer. The microwave absorption characteristics of Y2Co17@SiO2/PU were also investigated at various volume fractions. We not only investigate the zero-reflection conditions of the samples with different volume fractions, but also show that every absorber has a strong reflection loss value (RL ≤ −65.00 dB) and excellent microwave absorption properties with an average RL of Y2Co17@SiO2/PU being below −10 dB at 8 GHz–18 GHz under different thicknesses, showing that the enhancement of microwave absorption performance arises from the balance between permeability and permittivity of absorber.

As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y2Fe17. In order to regulate the electromagnetic parameters of absorbers, the Y2Fe17N3–δ particles were coated with silica (Y2Fe17N3–δ @SiO2) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (RLmin) was presented obviously. Compared to the microwave absorption properties of Y2Fe17N3–δ /PU absorber, Y2Fe17N3–δ @SiO2/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ( ε r / μ r ) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (RL < –10 dB) was derived and simplified. The calculated bandwidths agreed well with experimental results.

In this work, we have investigated the microscopic magnetic properties of c-axis oriented hcp-CoIr soft magnetic thin films (SMTFs) by using Mossbauer spectroscopy. We have found that the deviation of magnetic moments from the film plane slowly increases with increasing film thickness due to perpendicular magnetic anisotropy coming from the film growth procedure. Our results also suggest that optimizing the growth conditions at the initial stage of the film growth should be very important to further reduce this deviation. These results will be beneficial for further improving the soft magnetic properties of these SMTFs for functional electronic devices.

In this work, we report the investigation of microstructure and magnetic properties of the Co72Pt28/Pt/Co81Ir19 exchange-coupled composite (ECC) media using soft-layer (SL) of Co81Ir19 with negative magnetocrystalline anisotropy (MA). Our TEM images show that the hard-layer (HL) exhibits a columnar type microstructure with well-isolated grains and the exchange-coupled SL with hcp-structure show the same texture. Strong coupling of the two layers have been evidenced by the magnetic characterization for all the studied films with Pt inter-layer thickness ranging from 0 to 2 nm. Importantly, these ECC media films have much lower coercivities and much higher thermal stabilities in the favor of high-density magnetic recording.

In the present work, we have investigated both static and dynamic magnetic properties of c-axis oriented hcp- ( CoIr ) 100 - x Cr x soft magnetic thin films in great detail. We have found that the coercivity decreases much faster than the saturation magnetization with the increasing of Cr content in favor of better soft magnetic properties. Moreover, the in-plane and out-of-plane magnetic anisotropy can be greatly changed as a function of x. Therefore, the microwave magnetic properties can be tuned according to the requirements of different applications.

The electromagnetic parameters of magnetic unoriented and oriented Ce2Fe17N3-δ powders/Silicone composite with 15 vol% were investigated in the 0.1–18 GHz range. It was found that the initial permeability increased from 2.78 to 3.6 as well as the optimal RL reached –61.3 dB with a thickness of 1.91 mm at 9.01 GHz for the composite after orientation. The microwave absorbing properties of oriented composite were greatly enhanced resulting from the perfect impedance match condition improved by rotational magnetic orientation. This novel rotational magnetic orientation method might provide a new way to design high performance microwave absorbers.

A map displaying the reflection loss (RL) properties including the frequency and intensity for Co2Z barium ferrite composite was developed based on the matching model. In quarter-wavelength matching map, the number and the frequency positions of absorbing peaks presenting in RL curve for Co2Z barium ferrite composite with a certain thickness could be approximately predicted by quarter-wavelength matching model. From impedance map, the intensity of absorbing peaks in measured RL curves was analyzed. Moreover, the presence of absorbing peak in RL curve could be illustrated and understood physically and clearly using a picture of interference cancellation of two EM waves reflected by the absorber layer interface and a backed metal plate.

MnZn ferrite thin films are deposited by alternative sputtering technique from two targets with the composition of MnFe2O4 and ZnFe2O4, and the behavior of the magnetic properties of the MnZn ferrite thin films irradiated by Kr26+ ions at energy of 2.03 GeV is investigated by magnetization measurements. The fabricating and modifying conditions on the performance of the films are studied to improve Ms and reduce Hc of the films, making the films suitable to the applications of high-frequency film devices. For Mn1-xZnxFe2O4 thin films, the Ms increases firstly then decreases and Hc decreases monotonously with increasing Zn content. And both Ms and Hc are sensitive to Kr26+ ion irradiation and exhibit different behaviors depending on the ion fluence range. The modifications of the magnetic properties could be interpreted very well by the effects related to the stress and defects induced by SHI irradiation.

Fe/Al2O3 and Fe3Al/Al2O3 composites were prepared by mechanochemical synthesis. Microwave characteristics were measured in 0.1–18 GHz. A reflection loss (RL) exceeding -10 dB in the frequency range of 1.5-8.5 GHz for an absorber of 6-1.5 mm was achieved for the Fe3Al/Al2O3 composites. Optimal RL of -41 dB was obtained at 2.8 GHz for an absorber thickness of 3.9 mm. The good microwave-absorption properties results from a proper impedance match as a consequence of the insulator Al2O3 around Fe and Fe3Al. Microwave reflection results show that the corresponding frequency and the matching thickness is closely related to the quarter wavelength matching condition and these composites can be attractive candidates for electromagnetic wave absorption materials.

Fe-Co soft magnetic films with tuneable in-plane uniaxial anisotropy were successfully electrodeposited onto ITO conductive glass. The influence of composition and electrolyte temperature on in-plane magnetic anisotropy field was investigated. Our results show that the in-plane uniaxial anisotropy can be induced by a magnetic field applied in the film plane during electrodeposition. Fe-Co films with various Fe content in the range from 35 at.% to 53 at.% were obtained and the magnetic anisotropy field was very sensitive to the composition. Moreover, the influence of electrolyte temperature on magnetic anisotropy field was investigated and it was found that the in-plane uniaxial anisotropy field can be tuned by varying the electrolyte temperature from 5 to 40 oC.

In this work, the Z-type barium ferrite of single phase was prepared by the salt-molten method which was a novel, economical and environmentally friendly method. The results showed that the salt was helpful to get single phase and could effectively modify the shape of the powder. Based on the microwave measurement, reflection losses exceeding −20 dB of Co2Z composite were obtained in the frequency range of 4.1–14.5 GHz for absorber thicknesses of 2.1–3.5 mm and the minimum value of the reflection loss was -42.9 dB at 4.9 GHz for the thickness of 2.9 mm. For those unique properties, Co2Z could be a good candidate for electromagnetic (EM) materials and other practical applications at the high frequency.

In this paper, we report on the microwave absorbing properties of the Ni/SiO2 core/shell soft magnetic material which was synthesized by the tetraethyl orthosilicate (TEOS) hydrolysis method. The SEM patterns were shown that the particles of Ni/SiO2 were more dispersed and homogeneous. Microwave absorbing properties were measured in the range of 0.1–18 GHz. A reflection loss (RL) exceeding −20 dB in the frequency range of 2.6–8.9 GHz was achieved for an absorber thickness of 2.0–5.6 mm, and an optimal RL of −49.5 dB was obtained at 4.4 GHz for the thickness of 3.5 mm. The good microwave absorption properties resulted from a proper impedance match as a consequence of the insulator SiO2 around Ni particles.

For the sake of thinner electromagnetic wave absorbers used in quasimicrowave band, planar anisotropy carbonyl-iron (PACI) coated with amorphous SiO2 particles as absorber and paraffin as matrix were prepared. The complex permeability, complex permittivity and microwave absorption properties were investigated in the frequency range of 0.1-18 GHz. Both the real parts of permeability and permittivity are increased with the increasing of PACI/SiO2 particles volume concentrations. The minimum reflection loss shifts to the low frequency region with increase in PACI/SiO2 particles volume concentrations. The decrease of matching frequency could be well explained by the increasing of and . The PACI/SiO2 core-shell material exhibits great potential in application absorbers in quasimicrowave frequency range.

Polycrystalline magnetite (Fe3O4) thin films is synthesized at low temperature (90 oC) by electroless plating in aqueous solution, and the behavior of the magnetic property of the Fe3O4 thin film irradiated by Kr26+ ions at energy of 2.03 GeV is investigated by magnetization measurements. The initial crystallographic structure of the Fe3O4 remains unaffected after swift heavy ion (SHI) irradiation, but both coercive force and saturation magnetization are sensitive to Kr26+ ion irradiation and exhibit different behaviors depending on the ion fluence range. And SHI irradiation could make the magnetic moments of the Fe3O4 films ordered around the columnar defects and the magnetic moments tend to arrange along the films plane. All modifications of the magnetic properties could be interpreted very well by the effects related to the stress and defects induced by SHI irradiation.

The magnetic spectra of two magnetostatic coupled ferromagnetic stripes with different distances were investigated by the three-dimensional object oriented micromagnetic framework (OOMMF) code. The studied systems exhibit two resonance peaks. The higher peak can be identified with the bulk mode predicted by the macroscopic LL model. The lower peak originates from edge magnetic moments. Influence of magnetostatic interaction on the two resonance models was studied in detail. As the distance between two stripes increases, the magnetic spectrum of two stripes is close to the case of a single stripe.

FeNi nanotubes were successfully prepared in pores of anodic aluminium oxide templates by the wetting template method. By varying the deposition conditions and the parameters of the templates, the lengths and the outer as well as the inner diameters of the tubes can be tailored. The FeNi nanotubes and their arrays were characterized by transmission and scanning electron microscopy. Macroscopic magnetic measurements show the FeNi nanotube arrays to have obvious anisotropy, and the easy axis is parallel to the nanotube axis. The magnetic moment distributions in the tube walls and the magnetization reversal mechanism are discussed. Magnetic moments of the FeNi nanotube preferentially lie in the nanotube wall, but the distribution is spatially isotropic. These magnetic behaviours are due to the unique shape of the nanotube.

MgFe2O4 nanoparticles with different grain sizes were prepared by the low-temperature solid-state reaction method. The X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), superconducting quantum interference devices (SQUID) and 57Fe Mössbauer spectroscopy (MS) were used to characterize the structure, magnetic properties and surface anisotropy of nanoparticles. Oxygen parameters suggested that lattice distortion was decreased with reducing particle size. In comparison with the bulk material, smaller saturation magnetization (Ms) and larger coercive force (Hc) for nanoparticles were observed. The critical sizes for transition from multidomain to single domain and for superparamagnetic transition were estimated to be 25 nm and 28 nm, respectively. In summary, the fabricating conditions for the low-temperature solid-state reaction method are studied to improve Ms and reduce Hc of the films, making the films suitable to the applications of the magnetic targeted drug.

Thin films of CoFe2O4 spinel ferrite were prepared on silicon (100) substrates at low temperature by means of a modified polyvinyl alcohol processing, and the structure and magnetic properties as a function of the only one varied calcination temperature were investigated in detail and optimized. The CoFe2O4 ferrite films had a single phase spinel structure and were well-crystallized at temperature above 600 °C, which is much lower than the required temperature in the traditional ceramic method (about 1000 °C). The films annealed at and above 500 °C for 1h showed the grain sizes between 9 and 40 nm, and exhibited high coercivities and high saturation magnetization. Co-ferrite films prepared by sol-gel method and annealed at 700 °C had excellent potential for important technological applications, such as information storage and magnetooptical devices.

Fe3O4 and Fe nanowires are successfully fabricated by electrospinning method and reduction process. Wiry microstructures were achieved with the phase transformation from α-Fe2O3 to Fe3O4 and Fe by partial and full reduction, while still preserving the wire morphology. The diameters of the Fe3O4 and Fe nanowires are approximately 50–60 nm and 30–40 nm, respectively. The investigation of microwave absorption reveals that the Fe3O4 nanowires exhibit excellent microwave absorbing properties. For paraffin-based composite containing 50% weight concentration of Fe3O4 nanowires, the minimum reflection loss reaches −17.2 dB at 6.2 GHz with the matching thickness of 5.5 mm. Furthermore, the calculation shows that the modulus of the ratio between the complex permittivity and permeability |ε/μ| is far away from unity at the minimum reflection loss point, which is quite different from the traditional opinions.

The specific heat of S =1/2 frustrated Heisenberg antiferromagnetic spin ladder is investigated by means of a modified spin-wave theory. It is found that at low temperatures the specific heat shows a round peak, and decays exponentially below the peak temperature. The maximum of the specific heat decreases with increasing the rung-couplings, while it increases with increasing the diagonal couplings. The peak temperature moves to lower temperatures when the rung-coupling is increased, while it shifts to higher temperatures when the diagonal coupling is increased. Our observation is expected to be confirmed experimentally.

The nonlinear surface spin waves in ferromagnets with pure inhomogeneous exchange anisotropies have been considered. The boundary condition for magnetization of this system is derived. The nonlinear dispersion relation for these waves is obtained, and the modulation of the inhomogeneous exchange constants is investigated. The two-dimensional nonlinear Schrodinger equation satisfied by the spin-wave envelope amplitude is derived for the first time, and conditions for the existence of a single solitonic solution are discussed. A soliton solution is presented as an example.

The ligand 1-phenyl-3-methyl-5-hydroxy-4-pyrazolyl phenyl ketone (PMBP) isonicotinoyl hydrazone (H2L) was prepared by condensation of PMBP with isoniazid. Seven complexes of rare earth metals with H2L were synthesized and characterized on the basis of elemental analyses, IR, UV, 1H NMR spectra and thermal analyses. The general formula of the complexes is Ln(HL)3·3.5H2O (where Ln(III)=La, Eu, Gd, Tb, Dy, Ho and Er). X-ray diffraction analysis showed that the coordination polyhedron of the Eu complex is a tricapped trigonal prism. The La and Eu complexes possess antitumor activity, and the inhibitory rates for leukemia cells (L1210) are 87.1% and 78.5%, respectively.

The metastable 304 stainless steel film with BCC structure, fabricated by using a vapour quenching method, is strongly ferromagnetic. The effect of the local environment on the hyperfine parameters, and the influence of the heat treatment and pressure on stability in the metastable phase, were studied by means of conventional and high-pressure 57Fe Mossbauer spectroscopy. Each non-iron nearest-neighbour atom (Cr, Ni and Mn) of Fe atoms decreases the hyperfine field by an average of about 2.3 T and the isomer shift by about 0.01 mm s-1. Moreover, each non-iron next-nearest-neighbour atom is estimated to reduce the hyperfine field by an average of about 1.2 T. It is found that the transformation from the metastable BCC state to the FCC state begins near 500 degrees C and is completed near 800 degrees C. No FCC phase appears under a pressure smaller than 36 kbar. In both cases, however, the magnetization direction of the sample is observed to reorientate, and shows a stronger tendency to the out-of-plane after annealing and under pressures up to 8 kbar, while it is closer to the in-plane under pressures larger than 8 kbar.

Ultrafine (Fe0.7Co0.3)100−xBx amorphous powders with boron content x in the range of 27 to 40 at% are prepared by borohydride reduction without oxide of Fe3+ in the samples. With increasing boron content the average hyperfine field decreases and the average isomer shift increases. Comparing the hyperfine parameters of FeCoB powder with those of FeB powder having the same compositions, it can be seen that the average hyperfine fields and isomer shifts are quite different and the local environment of FeCoB powder is more complicated than that of FeB amorphous powder. DSC results indicated that the stability of the powder increases with increasing B content. Durch Borhydridreduktion werden ultrafeine, amorphe (Fe0.7Co0.3)100−xBx-Pulver mit einem Borgehalt von x im Bereich von 27 bis 40 At% hergestellt. In den Proben befindet sich kein Fe3+-Oxid. Mit wachsendem Borgehalt nimmt das mittlere Hyperfeinfeld ab und die mittlere Isomerverschiebung nimmt zu. Ein Vergleich der Hyperfeinparameter der FeCo;B-Pulver mit denen der FeB-Pulver mit gleicher Zusammensetzung ergibt, das die mittleren Hyperfeinfelder und Isomerverschiebungen vollig unterschiedlich sind und die lokale Umgebung der FeCoB-Pulver komplizierter ist als die der amorphen FeB-Pulver. DSC-Ergebnisse zeigen, das mit wachsendem B-Gehalt die Stabilitat der Pulver zunimmt.

Combining ME and NMR investigations of Nd2Fe14C compound, the hyperfine field values at 4.2 K and their assignment to the six Fe sites have been determined to be in following sequence: 26.8 (4e), 29.8 (4c), 30.9 (16k1), 31.6 (8j1), 33.9 (16k2), 36.9(8j2) Tesla(T). The Mossbauer measurements of the sample were carried out between 4.2 K and 300 K. It was found that a spin reorientation takes place at about 140–150 K and the canting angle is about 29.

The temperature dependence of the coercivity, Hc(T), at low temperatures in Dy(Fe0.94M0.1)2(M=Ga, Al), SmCo3.5Cu1.5, and Sm(CoCuFeTi)6.8 is interpreted in terms of a physical model in the framework of the quantum regime. It is believed that the motion of the narrow domain wall in the compounds is a quantum excitation and activation process, and it is also shown that the anomalies of Hc(T) at low temperatures in the hard magnets are due to the competition results of the quantum mechanical motion and the intrinsic scattering of their domain walls. Finally, the theoretical results are observed to be satisfactorily consistent with the experiments. Die Temperaturabhangigkeit der Koerzitivkraft Hc(T) von Dy (Fe0.9M0.1)2 (M=Ga, Al), SmCo3.5Cu1.5 and Sm(CoCuFeTi)6.8 bei niedrigen Temperaturen wird mit einem physikalischen Modell im Rahmen eines Quantenregimes interpretiert. Es wird angenommen. das die Wanderung der schmalen Domanenwand in den Verbindungen eine Quantenanregung und ein Aktivierungsprozes ist und cs wird auch gezeigt, das die Anomalien von Hc(T) bei niedrigen Temperaturen in den harten Magnetcn durch die Konkarrenzergebnisse der quantenmcchanischen Bewegung und der inneren Streuung ihrer Domanenwande verursacht wird. Die theoretischen Ergebnisse befinden sich in befriedigender Obereinstimmung mit den Experimenten.

The magnon excitations and magnetic properties of a theoretical model proposed for quasi one dimensional organic polymer ferromagnets are investigated. It is found that two non-degenerate magnons exist in the system, and their excitations are analog with those ones in ferrites. The specific heat, magnetization, and zero-field susceptibility of the system are also obtained, and found that the model shows some exotic behaviors. Es werden Magnonenanregungen und die magnetischen Eigenschaften eines fur quasi-eindimensionale organische Polymer-Ferromagnete vorgeschlagenen Modells untersucht. Es wird gefunden, das zwei nichtentartete Magnonen im System existieren und das ihre Anregungen sich in Analogie mit denen in Ferriten befinden. Die spezifische Warme, Magnetisierung und Nullfeld-Suszeptibilitaten des Systems werden ebenfalls erhalten, und es wird gefunden, das das Modell einige ungewohnliche Verhaltensweisen aufweist.

Carbide of composition Gd2Fe17Cx compound with higher carbon concentration x = 2 was successfully prepared by the melt quenching. Fe-57 Mossbauer spectra of the carbides (x = 0, 1, 2) were measured at room temperature, the results show that the changing tendency of average hyperfine field and isomer shift is consistent with that of the carbides with x < 1.5. The effects of the interstitial carbon atoms in the Gd2Fe17 compound on the hyperfine parameters were discussed.