Negative Permeability Materials Research Articles

Magnetostatic waves in metallic rectangular waveguides filled with uniaxial negative permeability media

The propagation characteristics of magneto-quasistatic waves, more commonly, known as magnetostatic waves in a long, metallic rectangular waveguide filled with a metamaterial slab are comprehensively investigated. The metamaterial slab consists of split-ring resonators as an anisotropic uniaxial medium with transversal negative effective permeability. Some analytical relations and numerical validations on the characteristics of these waves are presented. The results include the dispersion relations, mode patterns (field distributions) that can be supported by such media, and their corresponding cutoff frequencies, group velocities, power flows, and storage energies of magnetostatic waves. The findings from the present research study can be advantageous to advance the synthesis and development of negative permeability materials with peculiar features in guiding structures.

Static Negative-Permeability Metasurface to Transfer Volumetric Static Magnetic Field

Inspired by transformation optics, negative permeability materials enable the transfer of static magnetic fields to a distant location far away from the current source. This is useful for situations in which it is difficult to place a current source near the region where magnetic fields are required. However, existing artificial negative permeability materials are three dimensional (3D) and bulky. In this study, we theoretically design and experimentally demonstrate a metasurface with static negative permeability that displaces volumetric 3D magnetic fields to a distant region. The design overcomes the existing limitation because the dimensions of the structure are reduced to two, and the control of the magnetic field has an increased degree of freedom. The proposed method can be further extended to tools and strategies to precisely displace and/or manipulate dc or quasistatic magnetic fields in regions of interest for various applications such as medical care and measurement precision.

Theory of spoof magnetic localized surface plasmons beyond effective medium approximations

A homogeneous negative permeability sphere can support magnetic localized surface plasmons (MLSPs). Generally, negative permeability materials are metamaterial (MM) structures exhibiting very deep subwavelength spatial scales, whose effects may be detrimental in the near-field for those applications based on effective medium approximations. We suggest to overcome this fundamental limitation by demonstrating analytically that the electromagnetic spatial distribution, associated to a MLSP resonance and excited by a near-field source, can be accurately reproduced outside the sphere by substituting the negative permeability sphere with a homogeneous high-index dielectric one having the same radius. Considering that a large class of ferroelectric materials shows ultra-high dielectric constant and low-losses at low frequency (up to GHz), our spoof MLSPs theory could be a key tool for realizing high performance subwavelength magnetic photonic devices in the radiofrequency and microwave regions.

Waveguides including negative permeability and simultaneously negative permittivity and permeability materials for sensing applications

In this paper, a four-layer slab waveguide sensor is proposed. The waveguide has the conventional structure of a substrate, a guiding film and a cladding. At the substrate-film interface, an additional layer is inserted which can be a material with negative permeability or a material with simultaneously negative permittivity and permeability. The proposed waveguide is analyzed and both the dispersion relation and Fresnel coefficients are derived. The reflectance of an incident wave from the structure is investigated and plotted. The reflectance dip appearing in the profile is optimized. Using the two structures as optical sensor is also studied. The performance of the two structures as optical sensors is compared.

Refractometric sensor based on slab waveguides of simultaneously negative permittivity and permeability materials

A four-layer slab waveguide is treated analytically for optical sensing purposes. The layers of the waveguide are substrate, thin film and cladding. Another layer is introduced between the substrate and the film which is considered to have a negative permittivity or simultaneously negative permittivity (e) and permeability (μ). The structure is analyzed and the reflectance is deduced. The reflectance of p-polarized (TM) incident wave is investigated and plotted. A peak is observed in the reflectance profile which can be employed for sensing purposes. The reflectance peak is optimized to give the optimum parameters corresponding to the sharpest peak. The performances of the structures as optical sensors are examined and compared.

Controlling spins with surface magnon polaritons

Polaritons in metals, semimetals, semiconductors, and polar insulators can allow for extreme confinement of electromagnetic energy, providing many promising opportunities for enhancing typically weak light-matter interactions such as multipolar radiation, multiphoton spontaneous emission, Raman scattering, and material nonlinearities. These extremely confined polaritons are quasielectrostatic in nature, with most of their energy residing in the electric field. As a result, these ``electric'' polaritons are far from optimized for enhancing emission of a magnetic nature, such as spin relaxation, which is typically many orders of magnitude slower than corresponding electric decays. Here, we take concepts of ``electric'' polaritons into magnetic materials, and propose using surface magnon polaritons in negative magnetic permeability materials to strongly enhance spin relaxation in nearby emitters. Specifically, we provide quantitative examples with ${\mathrm{MnF}}_{2}$ and ${\mathrm{FeF}}_{2}$, enhancing spin transitions in the THz spectral range. We find that these magnetic polaritons in 100-nm thin films can be confined to lengths over 10 000 times smaller than the wavelength of a photon at the same frequency, allowing for a surprising 12 orders of magnitude enhancement in magnetic dipole transitions. This takes THz spin-flip transitions, which normally occur at timescales on the order of a year, and forces them to occur at sub-ms timescales. Our results suggest an interesting platform for polaritonics at THz frequencies, and more broadly, a way to use polaritons to control light-matter interactions.

Design of a modified single-negative metamaterial structure for sensing application

A new topology of modified negative effective permeability material (NEPM) are studied by adding a small similar form with different angles to the basic single split-ring resonators. We report our work conducted on the design, simulation and micro-fabrication of sensing system based on a modified split-ring resonator (MSRR) structure around 140 GHz operation frequency. Once the NEPM cells are excited, the reflection and transmission coefficients from the excitation mechanism can be measured by using quasi-optical technique with normal incidence. It has been shown that our proposal NEPM exhibits a high resonant frequency which is extraordinarily sensitive to the changes of the geometries and the properties of metal shape. By applying the new design of square Plus symbol (+) curve to the SRRs, more condensed size and higher sensitivity can be attained compared to conventional SRRs. Furthermore, the enhancement of sensitivity of the new design is also exposed. The considered sample double defect corner square modified form (DCD2) is fabricated in our lab using a conventional printed circuit board process with 2 μm aluminum and validated by comparing simulated profiles with measurements.

Artificial localized magnon resonances in subwavelength meta-particles

The interaction between electromagnetic waves and objects is strongly affected by the shape and material composition of the latter. Artificially created materials, formed by a subwavelength structuring of their unit cells, namely metamaterials, can exhibit peculiar responses to electromagnetic radiation and provide additional powerful degrees of freedom to the scatterer design. In particular, negative material susceptibilities give rise to strong resonant interactions with deeply subwavelength particles. While the negative electrical permittivity of natural noble metals manifests itself in localized plasmon resonant oscillations, negative magnetic permeability materials are rare in nature. Here, the concept of artificial magnon resonance in subwavelength objects with effective negative permeability, designed via the metamaterial approach, is demonstrated. Strong localized oscillations of the magnetic fields within an array of split ring resonators, forming a sphere, hybridize in a collective mode of the structure. As a result, a high scattering cross section, exceeding that of a steel sphere with the same radius by four orders of magnitude, was demonstrated. Scatterers, based on tunable resonances within artificially created materials, can find use in a broad range of electromagnetic applications, including wireless communications, radars, RFID, internet of things hardware, and many others.

A High Gain and Directivity Bow Tie Antenna Based on Single-Negative Metamaterial

This paper presents an antenna of loaded with metamaterial to enhance the gain and directivity of antenna to improve the performance of the ground-penetrating radar system (GPR). By adjusting the parameters of the antenna to change the antenna equivalent capacitance, inductance, and designed the operating frequency of 0.5GHz-1.2GHz ultra-wideband antenna. On the basis of this operating frequency, we also designed the corresponding negative permittivity and permeability materials, and realized the design and simulation of patch antenna and material working in the 1GHz frequency band. The high gain and directivity of the antenna loaded with single negative material are verified by simulation. Compared to the original antenna increased the maximum gain of 7dB, the direction has also been greatly improved.

Magnetic Illusion: Transforming a Magnetic Object into Another Object by Negative Permeability

We theoretically predict and experimentally verify the illusion of transforming the magnetic signature of a 3D object into that of another arbitrary object. This is done by employing negative-permeability materials, which we demonstrate that can be emulated by tailored sets of currents. The experimental transformation of the magnetic response of a ferromagnet into that of its antagonistic material, a superconductor, is presented to confirm the theory. The emulation of negative-permeability materials by currents provides a new pathway for designing devices for controlling magnetic fields in unprecedented ways.

Negative permeability in magnetostatics and its experimental demonstration

The control of magnetic fields, essential for our science and technology, is currently achieved by magnetic materials with positive permeability, including ferromagnetic, paramagnetic, and diamagnetic types. Here we introduce materials with negative static permeability as a new paradigm for manipulating magnetic fields. As a first step, we extend the solutions of Maxwell magnetostatic equations to include negative-permeability values. The understanding of these new solutions allow us to devise a negative-permeability material as a suitably tailored set of currents arranged in space, overcoming the fact that passive materials with negative permeability do no exist in magnetostatics. We confirm the theory by experimentally creating a spherical shell that emulates a negative-permeability material in a uniform magnetic field. Our results open new possibilities for creating and manipulating magnetic fields, which can be useful for practical applications.

Three-dimension isotropic negative permeability material made of eight-split-ring resonator

Based on a traditional split-ring resonator, a new type of eight-split-ring resonator structure, capable of providing negative permeability, is proposed in the paper. A three-dimension structure, consisting of three orthogonal eight-split-ring resonators, is a kind of three-dimension isotropic negative permeability structure. Simulation results show that in a three-dimensional space, the magnetic resonance behavior of three-dimensional structure is independent of electromagnetic wave direction and can give negative permeability at the frequency around 4.1GHz. Also, it is demonstrated that the orthogonal pattern in such three-dimension structure does not affect magnetic resonance behavior, facilitating structural analysis and material preparation. The paper provides a reference to the development of metamaterials towards multiple dimensions and directions.

负介电常数材料和负磁导率材料组成三明治结构的隧穿模

负介电常数材料和负磁导率材料组成三明治结构的隧穿模

Surface plasmon polaritons at the interface of form birefringence metal and the negative magnetic permeability material

The surface plasmon polaritons (SPPs) at the interface of form birefringence metal (FBM) and the negative magnetic permeability material (NMPM) are investigated. The dispersion relation and the characteristic length of the p- and s-polarized SPPs along the X and Y directions are discussed in detail, including the wavelength, the propagation distance, and the penetration depth into two media of SPPs in the range of 400–600 nm. It is shown that both p- and s-polarized SPPs can be observed at the interface formed by FBM and NMPM, and that their properties and characteristic length are very different along the X and Y directions. Especially, it is also found the maximum and minimum of characteristic length for the p- and s-polarized SPPs at certain wavelength.

Magnetic levitation from negative permeability materials

As left-handed materials and metamaterials are becoming more prevalent, we examine the effect of negative permeability upon levitation force. We first consider two half spaces of differing permeability and a point magnetic source, so that the method of images may be employed. We determine that the resulting force may be larger than for conventional magnetic materials. We then illustrate the inclusion of a finite sample thickness.

Negative refractive index designed in a periodic composite of lossy microplasmas and microresonators

A novel metamaterial with negative refractive index was designed using a spatially periodic composite of microplasmas and microresonators. Microresonators, which are double-helix metal wires in this report, work as an origin of macroscopic negative permeability material, as well as discharge electrodes. If a resonance frequency of the resonators is well below electron plasma frequency of the microplasmas where their permittivity is negative in the real part with a certain imaginary part, the macroscopic refractive index becomes negative just above the resonance frequency where the macroscopic permeability is negative, even if microplasmas are fairly lossy; due to such a loss or conductive component in permittivity, electromagnetic waves are not evanescent but propagating. This result indicates that plasmas can play important roles in parameter control of a metamaterial with a complex refractive index.

Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs

The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated.

Octagonal split resonant rings composite metal-wires to realize negative refraction

Traditional C-shaped split resonant ring(SRR) composite metal wire periodic structure is studied through simulation and experiment. Comparing the simulation result of negative permeability material based on periodic structure of octagonal SRR with that of closed split resonant rings (CSRRs), we ind that octagonal SRRs can produce negative permeability. A new kind of left-handed material combined with octagonal resonators and copper wires is de signed, and the simulation result shows that the structure has good left-hand property in a certain frequency band. Experimental samples of two different sizes are fabricated, in which negative refraction happens in ranges of 9.8—15 GHz and 9.5—15 GHz separately: small size sample has more broad negative band but lower transmission rate.By comparison with the experiment result of C-shaped sample we ind that the octagonal SRR hasa high transmission rate , but energy transmitting through new designed structure shows a more proportion in negative field, which demonstrates better negative behavior. This has important significance on design and study on new periodic structures of left-handed materials.

Omnidirectional reflection and flat-top transmissionin Thue-Morse quasicrystal with single-negative materials

By means of transfer matrix method, we investigate the transmittance and reflectance of Thue-Morse (T-M) structure composed of negative-permittivity and negative-permeability materials. It is shown that the width and location of an omnidirectional reflectance band remain invariant with the change of generation order, and that the omnidirectional reflectance band is determined by both TE and TM polarization, which different completely from that in dielectric T-M structure. Moreover, a flat-top total transmission band occurs around the same frequency in which the general zero average permittivity and permeability are both satisfied in T-M structure. The basis for these phenomena are presented and discussed.

Study on new periodic structures of left-handed material composed of hexagonal SRRs and metal wires

We studied new left-handed material composed of hexagonal split resonant rings （SRRs） based on trigonal resonators and metal wires through simulation and experiment. Simulated negative permeability material based on periodic structures of trigonal SRRs, in contrast to simulation result based on closed split resonant rings （CSRRs）, we found that the trigonal SRRs can generate negative permeability, and multilayer SRR simulation shows the coupling can enhance the resonant frequency and broaden resonant frequency band. We designed a new kind of left-handed material combined with hexagonal resonator based on trigonal resonators and copper wires. Simulation shows that the structures have good left-handed property. We have fabricated experimental samples which show negative refraction when the frequency lies in 93—108 GHz rangc. This has important significance on design and study of new types of periodic structures of left-handed materials.