Low Magnetic Loss Research Articles

Determination of Low Loss in Isotopically Pure Single Crystal 28Si at Low Temperatures and Single Microwave Photon Energy

The low dielectric losses of an isotopically pure single crystal 28Si sample were determined at a temperature of 20 mK and at powers equivalent to that of a single photon. Whispering Gallery Mode (WGM) analysis revealed large Quality Factors of order 2 × 106 (dielectric loss ~5 × 10−7) at high powers, degrading to 7 × 105 (dielectric loss ~1.4 × 10−6) at single photon energy. A very low-loss narrow line width paramagnetic spin flip transition was detected with extreme sensitivity in 28Si, with very small concentration below 1011 cm−3 (less than 10 parts per trillion) and g-factor of 1.995 ± 0.008. Such determination was only possible due to the low dielectric photonic losses combined with the long lifetime of the spin transition (low magnetic loss), which enhances the magnetic AC susceptibility. Such low photonic loss at single photon energy combined with the narrow line width of the spin ensemble, indicate that single crystal 28Si could be an important crystal for future cavity QED experiments.

A New Magnetizer for Measuring the Two-Dimensional Magnetic Properties of Nanocrystalline Alloys at High Frequencies

Nanocrystalline alloys are used extensively in high-frequency electromagnetic applications for their low magnetic losses and high saturation flux densities. To characterize their vector magnetic properties over a broad frequency range, a new magnetizer with a compact flux density-field B-H sensor was developed for two-dimensional testing up to 10 kHz.

연자성체를 이용한 저주파 무선전력전송 시스템의 누설 자기장 저감

This paper presents the electromagnetic shielding structure for low frequency wireless power transfer system with magnetic induction method using soft magnetic materials. Soft magnetic materials have advantages such as high permeability and low magnetic loss, but have undesirable effect of power loss by eddy current. To overcome this, we proposed the patterned soft magnetic material to suppress the eddy current path. For validity of this paper, we simulated the coil transfer efficiency and the radiated electromagnetic field, and fabricated the proposed structure using 79-permalloy. The measured results shows good agreements with the simulated results and reduction of the radiated electromagnetic field compared to commercial ferrite plate.

Greatly enhanced magneto-dielectric performance of the Ni0.5Zn0.5Fe2O4/polyvinylidene fluoride composites with annealed ferrite powders for antenna applications

Abstract

New ferrimagnetic garnets for LTCC-technology circulators

Abstract Yttrium Iron Garnet based ferrites are used in non-reciprocal devices like microwave circulators and isolators. The low dielectric and magnetic losses of those materials provide the required properties. The main drawbacks of circulators are their size and cost, due to complex mechanical assembling of the different materials. In order to simplify this complex manufacturing process, a possible solution would be to adapt the different materials to a common LTCC (Low Temperature Co-fired Ceramics) process: the circulators would be produced with an additive multilayer process. We showed that cationic substitutions (bismuth and copper) enable a considerable decrease of the sintering temperature of garnets, from about 1450°C to down to 950°C. Due to bismuth cations, a high permittivity is achieved allowing the reduction of the circulator size. Our most recent results show that it is possible to decrease this temperature down to 880°C, thanks to vanadium substitutions. This significant decrease of the sintering temperature leads to a compatible material for co-firing with gold and in particular with silver (melting point of 1064°C and 962°C respectively). Different assemblies of tapes were studied: ferrite with silver or gold, ferrite with dielectric and ferrite with dielectric and metallization. Physical analyses are exposed (dilatometry, coefficient of thermal expansion…) and magnetic and dielectric properties are discussed (permittivity and saturation magnetization). Moreover the first results of circulators in LTCC-technology with gold and silver screen printing are presented (transmission, isolation and return loss) and the compatibility of the different elements is analyzed.

Enhanced magnetocaloric effect in a Co-doped Heusler Mn50Ni37Co3In10 unidirectional crystal

A high-pressure optical zone-melting technique was employed to grow a Mn-rich Heusler Mn50Ni37Co3In10 unidirectional crystal in the present study. It was found that the Co-doped Mn50Ni37Co3In10 unidirectional crystal showed a low magnetic hysteretic loss and a widened working temperature interval in the vicinity of the martensitic transformation. The inverse magnetic entropy change (∆SM) reached 7.84Jkg−1K−1 around 237.5K under a magnetic field change of 30kOe, and the corresponding effective refrigeration capacity (RCeff) was about 127.2Jkg−1. The experimental results demonstrated a high potential to develop high-performance Mn-rich Heusler Mn–Ni–In magnetocaloric materials by means of Co doping in combination with the high-pressure optical zone-melting fabrication technique.

Low-loss Z-type hexaferrite (Ba3Co2Fe24O41) for GHz antenna applications

We report a low magnetic loss Ba3Co2Fe24O41 (Co2Z) hexaferrite for use in gigahertz (GHz) antennas. Acid-etching was very effective in removal of unwanted Y-type hexaferrite (Ba2Co2Fe12O22) from calcined Co2Z powder. It is found that the calcined and acid etched (AE) Co2Z hexaferrite shows a low magnetic loss tangent (tanδμ) of 0.012 and 0.037 at 1 and 2GHz, respectively. These low tanδμ are attributed to removal of Y-type hexaferrite, which possesses a lower anisotropy field (Hk) than W-type hexaferrite (BaCo2Fe16O27). The figure of merit (FOM) of the AE Co2Z hexaferrite is 141.7 and 48.7 at 1 and 2GHz, respectively. These FOM are much higher than the FOM of previously reported low-loss magnetic materials. Therefore, the AE Co2Z hexaferrite can be a good candidate for GHz antenna application in the ultra-high frequency (UHF) band.

Magneto-dielectric properties of doped ferrite based nanosized ceramics over very high frequency range

In the present study, indium doped nano sized nickel zinc cobalt based ferrite ceramics with composition Ni0.5Zn0.3Co0.2InxFe2-xO4 (x = 0.2 and 0.4) were synthesized by a co-precipitation technique. Powdered sample has been pre-sintered at 800 °C, pressed into toroids and finally sintered at 1000 °C. The single phase formation of the presintered powder has been confirmed by X ray diffraction (XRD). The average particle size of the presintered powder has been estimated by field emission scanning electron microscope (FESEM) and found to be about ~60 nm for x = 0.2 and ~80 nm at x = 0.4. The electromagnetic characterization has been made using vector network analyzer. High value of permeability (17.3 and 15.2 for x = 0.2 and 0.4 respectively) with low magnetic loss tangent of 10−1 order were obtained. Permittivity of 8.2 and 10, and dielectric loss tangent of the order of 10−2 were also achieved. With the measured electromagnetic parameters, miniaturization factor of 12.32 and normalized characteristic impedance close to unity (1.23) were obtained up to 100 MHz frequency. These fascinating parameters definitely propose Ni0.5Zn0.3Co0.2In0.4Fe1.6O4 ceramics as a substrate material for miniaturized antenna in very high frequency band. Possible reasons and mechanisms of electromagnetic properties for different concentrations of indium are discussed in the paper.

The Study of the Electrical Steel and Amorphous Ferromagnets Magnetic Properties

Materials with special magnetic characteristics are applied in various fields of industry. For instance, magnetic materials having the rectangular hysteresis loop are used in logics and computer science elements. In recent years, owing to obtained by the controlled crystallization from amorphous state nanomaterials properties studying, the soft magnetic materials with improved magnetic properties compared to the traditional amorphous alloys ones were obtained. The alloys possess the low coercive force and high magnetic permeability, besides, the above-mentioned materials have low magnetic reversal losses that provides their wide application as the transformer cores, pulse power supply sources. Magnetic materials along with semiconductors and dielectrics are important for electronic industry, therefore they require to be specially considered. Until recently such magnetic materials as crystal metal alloys, intermetallics and oxides (ferrites, etc.) were investigated. However, amorphous metals and alloys magnetism is intensively studied currently and some areas of amorphous magnets practical application are obviously observed. Nowadays, soft magnetic tape amorphous ferro- and ferrimagnetic materials representing the alloys of transitional metals and metalloids are widely used. The scientific problem of such materials obtaining by fast cooling from the liquid state is now becoming an important applied branch of engineering. One could confirm that the crystal magnetic materials era will be followed by the new magnetic metal materials era i.e. amorphous alloys. The object of the paper is the ferromagnetic materials magnetic characteristics studying through the digital method by the LabView software package applying. The description of normal magnetization curve control and measurement traditional methods (the magnetic induction dependence on the magnetic field intensity) is presented in the paper. The W-shaped core made of electrical steel and the ring-shaped one representing an amorphous alloy were used as the samples. The scheme of the experiment and its conducting description is offered. The hardware and software measuring complex was developed and the software allowing to obtain normal magnetization curve numerical values and to define the losses at magnetic reversal was implemented.

Wide Bandwidth CuO-Modified BaCoFeO Ferrite Antenna

This letter proposes a wide bandwidth monopole-like antenna, made from hexagonal Y-type ferrite Ba 2 Co 2 Fe 12 O 22 with CuO addition for the reception of terrestrial broadcasting, integrated services digital broadcasting (ISDB), allocated in the 470-770 MHz frequency band. The magnetic and electrical properties of the ferrite include a low magnetic loss of 0.05 with a relative permeability of 2.7 and an electrical loss of less than 0.01 with a relative permittivity of 14 up to 1 GHz, respectively. The proposed antenna has dimensions 3 × 3 × 30 mm 3 , is excited by a feedthrough conductor, and employs matching circuit elements to modify its impedance. Experimental results show that the proposed antenna has an average gain of - 1 dBi at a central frequency of approximately 600 MHz, and a wide frequency bandwidth of 300 MHz over the entire frequency range of the ISDB band at a gain level greater than - 5 dBi.

Magnon-phonon interconversion in a dynamically reconfigurable magnetic material

The ferrimagnetic insulator yttrium iron garnet (YIG) is an important material in the field of magnon spintronics, mainly because of its low magnetic losses. YIG also has very low acoustic losses, and for this reason the conversion of a state of magnetic excitation (magnons) into a state of lattice vibration (phonons), or vice versa, broadens its possible applications in spintronics. Since the magnetic parameters can be varied by some external action, the magnon-phonon interconversion can be tuned to perform a desired function. We present a quantum theory of the interaction between magnons and phonons in a ferromagnetic material subject to a dynamic variation of the applied magnetic field. It is shown that when the field gradient at the magnetoelastic crossover region is much smaller than a critical value, an initial elastic excitation can be completely converted into a magnetic excitation, or vice versa. This occurs with conservation of linear momentum and spin angular momentum, implying that phonons created by the conversion of magnons have spin angular momentum and carry spin current. It is shown further that if the system is initially in a quantum coherent state, its coherence properties are maintained regardless of the time dependence of the field.

Interview

Prof. Jeong-Hae Lee, from Hongik University in Korea, talks about the wireless power transfer efficiency improvement reported in the paper ‘Enhanced efficiency for wireless power transmission using an auxiliary loop on ferrite in metallic environment’, page 2039. Prof. Jeong-Hae Lee One of my research fields is to develop a highly efficient and compact resonator, which is the device transmitting and receiving the magnetic power, of a magnetic resonance wireless power transmission (WPT) system. WPT will be the key technology for future home appliances. Especially, it is thought that the wireless power transmission will be essential for the internet of things (IoT) in the near future. Therefore, a highly efficient and compact resonator for WPT systems needs to be developed for WPT to be practically applied to future electrical goods. Generally, the applications of WPT are home appliances because the aim of WPT is to remove the electrical wire for powering and to charge the batteries in them. As you know, these electrical products have at least one more ground plane. This is a critical problem when charging or powering the products because WPT uses the magnetic field to transmit the power. Especially, on the ground plane (or metallic plate), the inversed magnetic current is induced and this current also creates an inversed magnetic field. Thus, the total magnetic field for power transfer is weakened. So far, to prevent this effect, ferrites are mostly used between the ground and the resonator. The ferrites act as a reflector. Thus, the magnetic field does not see the ground plane with ideal ferrites. However, ferrites are lossy and, thus the efficiency of power transmission decreases. So there is a limitation on use of higher permeability material. To improve on the current shielding methods, we proposed an auxiliary loop patterned on the ferrite. This loop can be easily and simply fabricated, just patterning the single loop on the ferrite. In our Letter, we explained the design procedure in detail and proved its performance by measurement. Generally speaking, high permeability material has the better shielding characteristics. However, in current shielding methods, we cannot use a higher permeability material due to its high loss, so low shield effectiveness materials (low permeability and low magnetic loss tangent material) have to be used. With the proposed method, we could easily achieve the significantly improved performance just by applying the patterned loop on existing ferrite shields even though their permeability is lower. This method is suitable for any magnetic resonance wireless charging system. Of course, mostly, the charging systems have a ground plane. It is thought that the presented method in this Letter would be useful to enhance the charging efficiency. Also, the ferrite with an auxiliary loop could give an effectively high permeability; this concept might be applied for other applications which require high permeability with low loss. Our research group is working on the development of resonators for WPT systems such as compact resonators, beam steering resonators, mode reconfigurable resonators, and so on. Another research area is to develop small antennas and array antennas based on metamaterial transmission line. These metamaterial inspired antennas would be applicable for IoT devices, military systems, and RF wireless power transmission. This technology can improve the WPT efficiency significantly. So, in the next ten years, we would like to see commercialised products with this technology. Especially, the mobile charging systems would be the first application to adopt this. In addition, various home appliances would be equipped with this shielding technology for higher efficiency.

Influence of particle size on the magnetic spectrum of NiCuZn ferrites for electromagnetic shielding applications

The effect of ferrite particle size on the magnetic spectra (1MHz to 1GHz) of NiCuZn polycrystalline ferrites doped with Co2O3 and Bi2O3 were systematically investigated. The experiments indicate that the ferrite particle size tailored by grinding time and corresponding sintering temperatures is crucial to achieving high permeability, high Q-factor and low magnetic loss, at 13.56MHz for electromagnetic shielding applications especially in the near field communication (NFC) field. It is evident that high-performance NiZnCu ferrite materials are strongly tailored by morphology and microstructure. It is conclusive that fine ferrite particles and relatively low sintering temperatures are favorable to lowering magnetic loss and enhancing permeability. This work has built a foundation for improvement of the ferrite slurry used for fabrication of large area tape-casting ferrite sheets.

Industrialization of nanocrystalline Fe–Si–B–P–Cu alloys for high magnetic flux density cores

Nanocrystalline Fe–Si–B–P–Cu alloys exhibit high saturation magnetic flux density (Bs) and extremely low magnetic core loss (W), simultaneously. Low amorphous-forming ability of these alloys hinders their application potential in power transformers and motors. Here we report a solution to this problem. Minor addition of C is found to be effective in increasing the amorphous-forming ability of Fe–Si–B–P–Cu alloys. It allows fabrication of 120mm wide ribbons (which was limited to less than 40mm) without noticeable degradation in magnetic properties. The nanocrystalline (Fe85.7Si0.5B9.5P3.5Cu0.8)99C1 ribbons exhibit low coercivity (Hc)~4.5A/m, high Bs~1.83T and low W~0.27W/kg (@ 1.5T and 50Hz). Success in fabrication of long (60–100m) and wide (~120mm) ribbons, which are made up of low cost elements is promising for mass production of energy efficient high power transformers and motors

Production of new isotropic electrical steels at OAO NLMK

Specialists at OAO NLMK, in close collaboration with research institutes, have developed new grades of isotropic electrical steels and practical principles for their mass production, especially for use in high-efficiency magnetic cores. These include steels with low magnetic losses, high magnetic induction, and high magnetic permeability (high-permeability steel); semiprocessed rolled products from several alloying groups; and steel for high-speed stamping. The proposed technologies have no counterparts anywhere in the world and permit complete import substitution.

Microstructure and Texture Evolution in Non‐oriented Electrical Steels Along Novel Strip Casting Route and Conventional Route

In this article, evolution of microstructure and texture in non‐oriented electrical steels along novel strip casting route and conventional route are comparatively investigated in detail. It demonstrates the similar and important role of the microstructure and texture prior to cold rolling to finally obtain desirable recrystallization microstructure and texture in both routes. In both routes, a high intensity of cube‐fiber texture and a low intensity of γ‐fiber texture can be acquired in hot strips by optimizing the hot rolling and thermal treatment parameters. Accordingly, after cold rolling and annealing, a lower intensity of γ‐fiber texture together with a higher intensity of cube‐fiber texture, which are favorable for high‐permeability materials, can be obtained in both routes. The desired large grain size in the finally annealed materials to obtain low magnetic losses may be gained by choosing appropriate annealing conditions after the first stage of recrystallization. The features of microstructure and texture are similar at comparable stages. The main differences in the regarded different processing routes are in the practical efforts. The detailed results and deeply corresponding discussion on how the microstructure and texture develop during cold rolling and annealing in differently processed samples will be given in the future work.

Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

CaCu3Ti4−xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ′) as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

High frequency permeability and permittivity spectra of BiFeO3/(CoTi)-BaM ferrite composites

Low magnetic loss ferrite composites consisting of Ba(CoTi)1.2Fe9.6O19 and BiFeO3 (BFO) ferrite were investigated for permeability, permittivity, and high frequency losses at 10 MHz–1 GHz. The phase fraction of BiFeO3 was quantitatively analyzed by X-ray diffraction measurements. An effective medium approach was employed to predict the effective permeability and permittivity for the ferrite composites, which was found to be in good agreement with experimental data. The experiment demonstrated low magnetic losses (<0.128), modified by BFO phase fraction, while retaining high permeability (∼10.86) at 300 MHz. More importantly, the BFO phase resulted in a reduction of magnetic loss by 32%, as BFO phase increased from 2.7 vol. % to 12.6 vol. %. The effect of BFO phase on magnetic and dielectric properties revealed great potential for use in the miniaturization of high efficiency antennas.

Low loss Co2Z hexaferrite with matched permeability and permittivity in HF and VHF bands

Magneto-dielectric materials with matched permeability and permittivity have significant advantages for miniaturization and efficiency improvement of antennas. In this study, we adopted the Z-type hexaferrites in series (Ba0.5Sr0.5)3Co2Fe24O41+xSnO2 (where x=0, 0.1, 0.2, 0.4, and 0.6wt%) to produce the magneto-dielectric material. It was found that moderate SnO2 could obviously enhance mass transfer and densification of the ferrites, while there was no significant increase in grain size, which favored to obtain low magnetic and dielectric losses. However, excessive SnO2 led to the appearance of Co2W phase and slight decrease of sintered density. The samples with 0.1 and 0.2wt% SnO2 could obtain relatively high refractive index with real permeability and permittivity around 15. And the former presented the lowest magnetic and dielectric losses; the latter presented the best matched permeability and permittivity. Both of them are suitable for applications of antenna miniaturization between 3 and 300MHz (HF and VHF bands).

BiFeO3 tailored low loss M-type hexaferrite composites having equivalent permeability and permittivity for very high frequency applications

Co–Ti substituted M-type hexaferrite composites, consisting of Ba(CoTi)1.2Fe9.6O19 with various amounts of Bi2O3 (0–8wt%), were successfully synthesized by conventional ceramic processes. The effects of Bi2O3 upon the composite microstructure, magnetic properties, and magnetic and dielectric properties sintered at low temperatures were systematically investigated. The present studies aim to develop magneto-dielectric materials possessing equivalent values of permeability and permittivity, as well as low magnetic and dielectric losses, which allow for miniaturizing efficient antennas at the very high frequency band (VHF, 30–300MHz). The present experiments show that addition of BiFeO3, observed in the polycrystalline hexaferrite composites, acts to reduce loss factors (i.e., tan δμ/μ′=0.014, tan δε/ε′=0.00071) while concomitantly retaining high and equivalent values of permeability and permittivity (i.e., μ′∼12 and ε′∼12 at 300MHz).