Ferrite Slab Research Articles

Inkjet-Printed Ferrite Substrate-Based Vialess Waveguide Phase Shifter

Magnetically controlled waveguide-based phase shifters are desirable for their high performance, but are bulky and heavy, thus cannot be easily integrated with printed circuit board (PCB) based circuits. To tackle this, substrate-integrated waveguide (SIW) technology has been utilized, which brings the waveguide to a standard PCB, but requires large numbers of vias as well as multiple cavities in the substrate for ferrite slab placement. This implementation technique involves complex fabrication and yields a relatively low figure of merit (FoM). To alleviate this, we present the first completely vialess ferrite substrate-based waveguide phase shifter realized through low-cost inkjet printing technique. All the four sides of a yttrium iron garnet (YIG) substrate have been metalized through inkjet printing, allowing the fabrication of a conventional rectangular waveguide on a standard magnetic substrate. The prototype has been tested in symmetric as well as antisymmetric modes of biasing and peak FoMs of 160°/dB at 7.22 GHz and 332°/dB at 7.46 GHz have been measured, which are higher than those of the previously reported designs. This all-around inkjet printing approach can open the door to low-cost, integrable magnetic phase shifters with excellent RF performances.

Design of Frequency-Reconfigurable Antenna on Dielectric and Magnetic Metamaterial Composite Substrate

Reconfigurable planar antennas are essential in multifunctional wireless communication devices. This letter presents the design of a frequency-reconfigurable patch antenna printed on a composite substrate made of a dielectric and a magnetic metamaterial (MMM). The MMM comprises magnetized ferrite slabs with embedded split-ring resonators (SRR). The constructive coupling between the resonances of the magnetized ferrites and SRR is optimized to achieve promising reconfigurable properties. The proposed frequency-reconfigurable antenna demonstrates a 158% increase in the frequency tuning range. Furthermore, the simulated results are experimentally verified, and the composite substrate shows slight effects on the antenna radiation characteristics.

Bandwidth Enhancement of a Mobile Phone Antenna Using Ferrite Slab

A novel technique to enhance the bandwidth of mobile phone antennas using YIG ferrite is proposed. The technique is applied in two slot antennas which are the proposed antenna and the reference antenna. The two antennas have the same shaped slot consisting of a rectangle connected to a circle etched on the ground plane. A ferrite slab is attached at the region near the circular slot on the ground plane of each antenna. The measured bandwidth of the proposed antenna with ferrite slab is enhanced to 0.669–1.533 and 1.69–5 GHz compared with the bandwidth of 0.81–1.44 and 2.3–5 GHz for the antenna without ferrite. The bandwidth of the reference antenna with ferrite slab is enhanced to 0.715–5 GHz compared with the bandwidth of 0.813–1.01, 1.11–1.3 and 2.33–5 GHz for the antenna without ferrite loading. The technique has the virtues of easy fabrication and low cost.

Ultra-broadband near-field magnetic shielding realized by the Halbach-like structure

With the great developments in electronic communication technology and miniaturized electromagnetic devices, near-field magnetic shielding has attracted much attention. However, for the widely used natural magnetic shielding materials, metal and ferrite, they have the unique limitations of large Ohmic loss and heavy weight, respectively. Although a compromise solution of the shielding layer may resort to the composite structure with metal and ferrite slabs, practical magnetic shielding with broadband, high efficiency, and ultra-thinness has remained a great challenge. In this work, inspired by the effective magnetic flux path established by the Halbach array, which is constructed by stacking permanent magnet in diverse directions, we propose a physical mechanism of local magnetic moment control in artificial structures, called the “Halbach-like structure.” We demonstrate the highly efficient and ultra-broadband near-field magnetic shielding in the Halbach-like structure with patterned metal and ferrite structures. By ingeniously designing the local magnetic moment, our structure not only provides an effective method for realizing high performance magnetic shielding but also paves the way to the other near-field controls, such as the wireless power transfer, wireless communications, and magnetic resonance imaging.

Bandpass Simulation of Anisotropic Magnetized Ferrite Material With Alternating Direction Implicit Scheme in Open Region

Stability of explicit finite-difference time-domain (FDTD) algorithm is limited by the established relationship which results in computation duration unacceptable in certain circumstances. To enhance the development of FDTD algorithm, unconditionally stable scheme is implemented to overcome such problem, especially for the open region simulation. Here, for bandpass simulation of anisotropic magnetized ferrite material, complex envelope (CE) method and its modified scheme are employed into the implementation. Generally speaking, the proposed scheme incorporates the alternating direction implicit (ADI) with the CE method during the simulation obtaining the bandpass ADI form in perfectly matched layer (PML) regions. Meanwhile, the proposed scheme establishes the bandpass calculation method of constitutive relationship in ferrite material regions. Such method can also be employed into the unmagnetized isotropic materials and other media. Through ferrite slab model and ferrite waveguide structure, accuracy, absorption, and efficiency are demonstrated in the bandpass open region simulation numerically. The proposed scheme can not only benefit an impressive performance but also maintain both stability and accuracy with decrement of iteration steps which can be proved to be an unconditionally stable implementation. Meanwhile, it also alleviates time increment problem within implicit schemes of small time steps. Thus, benefits of the proposed scheme can be summarized from the following categories: 1) enhanced absorption and efficiency for the ADI procedure; 2) decrement of duration with a small time step; 3) bandpass form inside the magnetized ferrite material; and 4) extensively employment in different kinds of materials.

A Tunable Ferrite Isolator for 30 GHz Millimeter-Wave Applications

In this article, a tunable ferrite-loaded isolator working at millimeter-wave (mm-Wave) frequency for applications in multi-function systems is presented. The device is based on nonreciprocal coupling between a ferrite slab and a half-mode substrate-integrated waveguide (HMSIW). The HMSIW offers a compact design and, more important here, the ability of energy coupling to adjacent resonators. The ferrite slab is placed outside the HMSIW, close to the H-wall symmetry of the HMSIW, providing the possibility of movement for the ferrite slab and low insertion loss of the transmission mode. Any change in the position of the ferrite slab changes the propagation constant of the mode traveling across the ferrite-coupled HMSIW, which, consequently, results in different center frequencies of the isolation. To the best of our knowledge, the proposed design is one of the first tunable isolators for such a high frequency. Despite previously reported isolators that require a strong magnetic bias field for mm-Wave range applications, the proposed isolator requires a relatively low magnetic bias (less than 20 KA/m), which is provided by a small and lightweight permanent magnet. The 10 dB isolation bandwidth of the design is about 2 GHz varying from 34 to 37 GHz based on the position of the ferrite slab. The insertion loss of the device is measured between 2 and 3 dB.

Significant enhancement of magnetic shielding effect by using the composite metamaterial composed of mu-near-zero media and ferrite

The magnetic shield plays an important role in magnetic near-field control. However, the requirements of efficiency, ultra thinness, lightness and cheapness are still the challenges. Here, we firstly propose a composite metamaterial in which the mu-near-zero media is covered with a ferrite slab. We verify that this structure can enhance the shielding effectiveness (SE) in a small area. Furthermore, we optimize the magnetic path by changing the bulk ferrite slab into a patterned slab. In this way, significant SE enhancement can be achieved in a large area. Experimental results show that the maximum SE of the composite metamaterial with a patterned ferrite is 20.56 dB, which is nearly 19 dB higher than that of a single ferrite slab with the same thickness of the composite metamaterial. The results on the composite metamaterial would be very useful in the applications involving magnetic shielding.

Nonreciprocal Isolating Bandpass Filter With Enhanced Isolation Using Metallized Ferrite

The nonreciprocal bandpass filter has been achieved by utilizing the nonreciprocity characteristics of the magnetostatic surface wave (MSSW) in planar ferrite slabs. In this article, the dispersion relation, impedance, and attenuation of MSSW between the pure and metallized ferrite slabs have been analyzed and compared. Theoretical analysis indicates that the ferrite slab metallized by a thin conductive layer would introduce significant attenuation on the metallized interface, which is MSSW propagating on the isolated direction, while MSSW on the other surface is barely affected. Therefore, nonreciprocal bandpass filter with enhanced isolation can be achieved with metallized ferrite slab. Simulated S-parameters show that a notch in the isolating direction can be obtained at the passing band of the transmitting direction. Experimental results show that the nonreciprocal filter with metallized yttrium iron garnet (YIG) slab (by depositing 100- $\mathbf {nm}$ copper film) exhibits more than 10-dB higher isolation than that with pure YIG slab, while the center frequency, insertion loss, and 3-dB bandwidth maintain almost the same. The center frequency of the filter with metallized YIG slab can be tuned from 7.26 to 8.38 GHz with insertion loss of less than 3 dB, and in-band isolation of more than 30 dB as the dc bias magnetic field is increased from 1.8 to 2.3 kOe. Besides, the nonreciprocal filter has ultra-wide out-band suppression since it utilizes the narrow frequency band of MSSW. The −10-dB out-band rejection exceeds 36 GHz in the upper band and 1 MHz in the lower band.

One-Way Leaky-Cladding Meta-Waveguides Based on Accidental Dirac Cones

Nonreciprocal waveguides play an important role in microwave and optical systems. Here we present a new concept for a one-way meta-waveguide: a waveguide that supports a guided mode in one direction while waves traveling in the opposite direction leak out into the waveguide cladding. This is achieved by placing a metasurface atop of a ferrite slab, and judiciously phase matching two radiant and one subradiant meta-waveguide modes in order to enhance the magneto-optical response and to create an accidental Dirac cone in the reciprocal space. By applying an in-plane magnetic field, the reciprocal and nonreciprocal contributions to magneto-optical response can interfere constructively/destructively depending on the propagation direction, thereby shifting the apex of the Dirac cone and creating a one-way propagation bandgap. The idea of one-way leaky-cladding waveguide provides an alternative way of designing nonreciprocal devices that do not require a gap in the Dirac cone.

Enhancing the spin Seebeck effect by controlling interface condition in Pt/polycrystalline nickel ferrite slabs

The spin Seebeck effect (SSE) is an emergent thermoelectric phenomenon, which enables a thermal-to-electrical energy conversion via the thermal injection of spin currents from a ferromagnet (FM) into an attached paramagnetic metal (PM). Recent studies have revealed that the SSE is very sensitive to the PM/FM interface condition, suggesting a potential way to enhance the SSE by controlling the interface condition. However, most of the previous studies are limited to conventional Pt/bulk single-crystal or thin-film YIG systems, lacking consideration for mesoscale surface defects such as pores and grain grooves, which frequently exist in more prevalent bulk polycrystalline magnets. Here, we investigate the effect of interface condition on the longitudinal SSE (LSSE) in a Pt/polycrystalline NiFe2O4 (NFO) slab system. Different interface conditions are induced by treating the surface of NFO slabs with varying combinations of polishing force (Fp) and post-annealing temperature (Ta) before the Pt deposition. The resultant LSSE signals show strong correlations with different interface parameters. In particular, we find that mesoscale surface defects (cracks, pores, and grain grooves) and the surface roughness play a crucial role in determining the magnitude of LSSE signals and demonstrate that those parameters can be deliberately controlled by properly choosing Fp and Ta. We report one sample with a spin Seebeck coefficient of 0.58 μV/K, which is significantly larger than that of bulk polycrystalline magnets reported thus far.

Tunable PDEBG using ferrite‐based metasurface for WiMaX application

This article presents a tunable ferrite-based anisotropic reflective metasurface, which provides a method to manipulate the TE and TM polarized waves separately, and has much stronger ability to control electromagnetic waves and provides different phase difference between two reflected polarized waves. This eventually leads to various polarized reflected waves starting from linear polarization to RHCP and LHCP. Ferrite slab is used for realizing anisotropic behavior. A novel method for tunability of single polarization response is observed. A wired dipole antenna operating at 3.5 GHz is designed above metasurface at height d. 95 k A/m of DC biasing is applied in both X and Y directions in ferrite-based metasurface to obtain RHCP and LHCP reflected waves from linearly polarized incident waves from metasurface. Moreover, polarization switchable dipole antenna is realized by changing the biasing direction. Furthermore by varying biasing, tunability of AR is realized from 3.3 to 4 GHz. The metasurface is simulated and designed on HFSS v.16.

Effects of rolling and coiling temperature on the microstructure and mechanical properties of hot-rolled high strength complex phase steel

The effects of rolling and coiling temperature on the microstructure and mechanical properties of complex phase hot-rolled high strength steel were investigated by varying rolling temperature and coiling temperature. The results showed that the strengthening of steel is mainly due to the combination of precipitation hardening and grain refinement. With the finish rolling temperature decrease, the accumulation of local strains promote the transformation from austenite to ferrite during coiling process, making ferrite grain more fine and homogeneous. With the coiling temperature decrease, the width of ferrite slabs and the average size of martensite/austenite islands (M/A islands) decrease, the main strengthening method is transformed from precipitation strengthening to fine grain strengthening. The final rolling temperature at 890 °C and coiling at 550 °C was found to provide a good combination of tensile and elongation properties.

Distribution of TiN inclusions in Ti-stabilized ultra-pure ferrite stainless steel slab

In order to clarify and control the silver defect on surface of cold-rolled sheet of the Ti-stabilized ultra-pure ferrite stainless steel, the distribution of TiN inclusions on the cross section of hot-rolled plate was studied using automated scanning electron microscopy/energy-dispersive X-ray spectroscopy inclusion analysis (ASPEX 1020 system). It was found that the number density decreases sharply from the surface to the center of the hot-rolled plate, whereas the average size increases. Then, the distribution of TiN inclusions on the cross section of continuously cast slab was investigated. Similarly, numerous small-sized TiN inclusions were generated at the subsurface of the slab. The average size rapidly increased and the number density dramatically decreased from the subsurface to 1/4 thickness, while from 1/4 thickness to 1/2 thickness, the increase in average size and the decrease in number density were slight. Thermodynamics results showed that TiN inclusion was formed below the liquidus temperature, which indicated that TiN inclusions could not be formed during secondary refining. Considering the microsegregation of solute elements and the equilibrium of TiN formation during solidification, TiN precipitated in the mushy zone when the solid fraction was close to 0.2. The growth of TiN was analyzed based on the diffusion-controlled growth model. With the increase in cooling rate, the time for TiN growth decreased and the size of TiN inclusions was diminished, which revealed the size distribution of TiN inclusions in the cast slab qualitatively.

A hybrid shielding structure for reduction of the leakage magnetic field in wireless power transfer system

AbstractIn this paper, we propose a hybrid shielding structure for the reduction of the leakage magnetic field in the wireless power transfer (WPT) system operating at 175 kHz. This structure consists of ferrite slab staked on the aluminum plate. The improvement in the magnetic field reduction is achieved, while minimizing the power transfer loss by optimizing the design parameters. The power transfer efficiency and leakage magnetic field are analyzed and verified through simulation and experiment. The experimental results show 77% power transfer efficiency with proposed structure, while the normalized leakage magnetic field strength was reduced up to 80% compared with the conventional shielding structures.

Cutoff Angles of the Backward Spin Wave in a Tangentially Magnetized Ferrite Plate

The cutoff angles for the wave vector and the group velocity vector of a backward spin wave propagating in a tangentially magnetized ferrite plate are calculated. It is established that the expressions for these angles do not depend on the mode number and coincide with the analogous expressions for the corresponding cutoff angles of a spin wave in an unbounded ferromagnet. It is found that the regions corresponding to all possible orientations of the wave vector for the backward and surface spin waves in a ferrite slab and for a spin wave in an unbounded ferromagnet are adjacent and nonintersecting. It is shown that, if the isofrequency dependence of the wave has inflection points, then the range of all possible orientations of the group velocity vector of the wave can be wider than the angular interval enclosed between the cutoff angles for the group velocity vector.

Cutoff Angles for the Group Velocity and Wave Vectors of a Backward Spin Wave in a Tangentially Magnetized Ferrite Slab

Based on an analysis of the dispersion relation for a backward spin wave in a tangentially magnetized ferrite slab, expressions are obtained that describe the cutoff angles of the wave and group velocity vectors for all modes of this wave.

Integrated Broadband Edge-Guided Mode Isolator With Antiparallel Biasing of the Ferrite Slabs

In this letter, a novel configuration of the integrated waveguide edge-guide (EG) isolator, containing two antiparallelly biased ferrite slabs separated by a dielectric gap (DG), is reported. It is found that in this configuration the transmission losses are significantly lower than the ones observed in an EG mode isolator completely filled with ferrite (without a DG). The principle of operation of the proposed isolator is analyzed numerically and the obtained low losses originate from the wave transmitted in the gap. This behavior is also demonstrated using the prototype of this type of isolator working at 6.25 GHz, where simulated and measured results show isolation of 48 dB and insertion losses of 1.3 dB.

Steerable Electromagnetic Transmission of Metal Gratings on a Magnetized Ferrite Slab

This paper presents a rigorous analysis of electromagnetic scattering and transmission of metal gratings on a magnetized ferrite slab. The Fourier transform is used to represent the electric and magnetic fields in the spectral domain. The mode-matching technique is enforced to obtain two simultaneous equations for the modal coefficients of each slit region. Numerical results show that the metal gratings on the magnetized ferrite slab exhibit a steerable electromagnetic transmission property depending on the applied dc magnetic field and the saturation magnetization of ferrite material.

Nonlinear TE surface waves in a ferrite slab bounded by Kerr-type metamaterials

In this paper, nonlinear transverse electric surface waves in a structure consisting of a ferrite slab sandwiched between a Kerr-type double-negative metamaterial (DNG-MTM) have been investigated. In addition to a DNG-MTM, two special cases with nonlinear single-negative metamaterials (SNG-MTMs) have also been discussed. The dispersion relations are obtained by applying the boundary conditions to the tangential field components of each layer. The propagation characteristics are plotted numerically for the effective wave index versus propagation frequency.

Distribution of the amplitude of the magnetic potential of diffractive beams generated in a ferrite slab by a surface spin wave incident on a slit in an opaque screen

The total magnetic potential generated in the far field of a ferrite slab as a result of a plane noncollinear surface spin wave incident on a slit in an opaque screen is investigated. The dependence of the potential amplitude from the polar angle in the plane of a ferrite slab is calculated for different orientations of the screen with relative to an external magnetic field magnetizing the slab. It is found that two diffractive beams are generated in the slab as a result of spin diffraction on the slit. The angular width of each beam depends largely on the slit’s orientation and can be greater or smaller than value λ n /D (where D is the slit’s width and λ n is the length of the spin wave corresponding to each beam).