Magnetorefractive Effect Research Articles

Vector magnetic field characteristics of magneto-shape effect with high figure of merit based on fiber optic vernier effect

The vector magnetic field structures utilizing magnetic fluid (MF) mainly rely on the magneto-refractive index effect (MRI), which has the low spatial resolution due to the long sensitive length. In this article, the vector magnetic field characteristics of the magneto-shape effect (MSE) are simulated and experimentally studied based on the fiber optic vernier effect. The high vector magnetic field sensitivity can be achieved under the condition of Φ128*73 μm in the sensitive area by combine the MSE and vernier effect. The distribution of magnetic field on the concavity of MF varies with magnetic field direction, giving rising to MF concavity different deformations. The magnetic field observation structure based on fiber optic vernier effect are fabricated to verify the vector magnetic field characteristics of MSE. The observation structure is subjected to one-dimensional and two-dimensional magnetic field. The test results demonstrate that the magnetic field sensibility can reach 2.36 nm/Gs, 3.88 nm/Gs and 4.52 nm/Gs under 0–55.0 Gs, 55.0–91.7 Gs and 91.7–119.2 Gs in Y direction field. The magnetic field sensibility is 0.91 nm/Gs in Z direction field. The magnetic field direction sensitivity can reach 1.16 nm/° in XY dimensional field. The structure of the MSE is very compact and the size is very small, which is very helpful for detecting the narrow space and gradient magnetic field.

An insight into the magneto-refractive effects of terbium-doped silica optical fibers used in magnetic field sensors

In this study, the magneto-refractive effect (MRE) of a terbium-doped fiber (TDF) that can be employed for magnetic field sensing was investigated. A microscopic model of a terbium doped magneto-refractive silica fiber was proposed, and the relationship between the refractive index (RI) of the fiber and its magnetic field was numerically studied. The MRE of the TDF was then characterized using an electronic holographic magneto-refractive measuring system. The characterization results showed that the RI of the TDF increased linearly at a rate of 2.13 × 10−5 RIU/mT as the magnetic field intensity increased from 0 to 10 mT. An all-solid-state magneto-refractive measurement system based on a fiber-optic Sagnac interferometer was designed for magnetic field sensing, which linearly responded to the applied magnetic field. The relationship between the dielectric tensor and magnetic moment of the fiber was analyzed. Based on the finite difference algorithm, the change in the RI and dielectric tensor of the optical fiber under a magnetic field was simulated. Results indicated that the proposed fiber has potential use in high-sensitive magnetic field sensing applications.

Magnetorefractive effect in metallic Co/Pt nanostructures

Objectives. To carry out a theoretical investigation of the features of magnetorefractive effect for metal-to-metal nanostructures. This study uses the example of multilayer Co/Pt nanostructures (ferromagnetic metal–paramagnetic metal) with a different ratio of ferromagnetic and paramagnetic phases in the visible and near-infrared (IR) spectral regions.Methods. The dependence was expressed explicitly using the basic formulas for permittivity, refraction and extinction coefficients, and optical conductivity. This then confirms the common nature of these two effects. The magnetorefractive effect for s-polarization of light was calculated using Fresnel formulas for a three-layer structure. This took into account the thickness of the samples and the influence of the substrate. Effective medium methods were used to calculate the dielectric permittivity of materials. Since the average range of cobalt concentrations was being studied, the Bruggeman approximation was used to establish the effective permittivity of nanostructures. The reflection coefficient at normal incidence was calculated for all nanostructures.Results. Since the permittivity of inhomogeneous samples was replaced by a common effective parameter depending on the permittivity of each component, we were able to apply the Drude–Lorentz theory for conductors in a high-frequency alternating field and then estimate the parameters of the electronic structure of the samples being studied. Plasma and relaxation frequencies were calculated for each sample. This made it possible for the number of free electrons to be estimated and scattering in nanostructures to be investigated.Conclusions. It was shown that Langmuir shielding can be observed in the given energy range in the IR region of the spectrum. The calculated values correlate well with the experimental data.

Strain-magneto-optics: Magnetoreflectivity in MnFe2O4 ferrite-spinel crystal

The single crystal of ferromagnetic magnetostrictive spinel MnFe2O4 was grown by the zone-floating method. The magnetic, magneto-elastic, optical, and magneto-optical properties of the MnFe2O4 ferrite-spinel were investigated in the infrared spectral range. A strain-magneto-optical phenomenon, which demonstrate the connection between magnetoreflection of non-polarized light and magnetostriction of MnFe2O4, was revealed. A maximum magnetoreflection of up to 1 % was observed at room temperature in a magnetic field of 2 kOe. Using the Kramers-Kronig method, the magnetorefractive effect and magnetooptical conductivity of MnFe2O4 were also calculated. The observed correlation between magnetoelastic and magneto-optical properties of MnFe2O4 was attributed to the significant contribution of linear magnetostriction to the magnetic anisotropy constant (ΔK/K1 ∼ 8 %) in the MnFe2O4 crystal. Additionally, a criterion of ΔK/K1 ∼ 1 % was proposed to evaluate the potential use of magnetostrictive materials in strain-magneto-optics.

Optimization Research of Er-doped Magneto-refractive Photonic Crystal Fiber Based on Surface Plasmon Resonance

In order to meet the demand for large-scale magnetic field testing, this paper proposes a D-shaped magneto-refractive photonic crystal fiber (MRPCF) based on surface plasmon resonance (SPR) by using the erbium-doped material. By varying the diameter, location, and number of layers of the air holes, the four different Models A, B, C, and D structures are created, and the corresponding magnetic field sensing properties are analyzed. The simulation findings demonstrate that the magnetic field sensitivities of Models A, B, C, and D are 28 pm/mT, 48 pm/mT, 36 pm/mT, and 21 pm/mT, respectively when the magnetic field strength is 5 - 405 mT. Meanwhile, the figure of merit (FOM) of the four MRPCF-SPR sensors is investigated, which have FOMs of 4.8×10-4 mT-1, 6.4×10-4 mT-1, 1.9×10-4 mT-1, 0.9×10-4 mT-1. Model B has high sensitivity and large FOM. It shows that altering the structural design of the fiber can significantly improve the magneto-refractive effect of MRPCF. The proposed MRPCF has numerous uses in the areas of geological research, earthquake and tsunami monitoring, and military navigation. It can also be expected to enable quasi-distributed magnetic field sensing.

Research Progress on Magneto-Refractive Magnetic Field Fiber Sensors

The magnetic field is a vital physical quantity in nature that is closely related to human production life. Magnetic field sensors (namely magnetometers) have significant application value in scientific research, engineering applications, industrial productions, and so forth. Accompanied by the continuous development of magnetic materials and fiber-sensing technology, fiber sensors based on the Magneto-Refractive Effect (MRE) not only take advantage in compact structure, superior performance, and strong environmental adaptability but also further meet the requirement of the quasi-distributed/distributed magnetic field sensing; they manifest potential and great application value in space detection, marine environmental monitoring, etc. Consequently, the present and prevalent Magneto-Refractive Magnetic Field Fiber Sensors (MR-MFSs) are briefly summarized by this paper, proceeding from the perspective of physicochemical properties; design methods, basic performance and properties are introduced systematically as well. Furthermore, this paper also summarizes key fabrication techniques and future development trends of MR-MFSs, expecting to provide ideas and technical references for staff engaging in relevant research.

Design of an Er-doped surface plasmon resonance-photonic crystal fiber to improve magnetic field sensitivity.

In order to meet the demand for large-scale magnetic field testing, this paper proposes a D-shaped magneto-refractive photonic crystal fiber (MRPCF) based on surface plasmon resonance (SPR) by using the erbium-doped materials. The four different structures of Models A, B, C, and D are designed by changing the diameter, the position, and the number of layers of the air holes, and the corresponding magnetic field sensing characteristics are analyzed. The results show that in the magnetic field range of 5-405 mT, the magnetic field sensitivities of Models A, B, C, and D are 28 pm/mT, 48 pm/mT, 36 pm/mT, and 21 pm/mT, respectively. Meanwhile, the figure of merit (FOM) of the four MRPCF-SPR sensors is investigated, which have FOMs of 4.8 × 10-4 mT-1, 6.4 × 10-4 mT-1, 1.9 × 10-4 mT-1, 0.9 × 10-4 mT-1. Model B has higher sensitivity and larger FOM. In addition, the effect of the structural parameters of Model B on the sensing performance is also studied. By optimizing each parameter, the magnetic field sensitivity of the optimized Model B is increased to 53 pm/mT, and its magneto-refractive sensitivity and FOM are 2.27 × 10-6 RIU/mT and 6.2 × 10-4 mT-1, respectively. It shows that the magneto-refractive effect of MRPCF can be effectively enhanced by optimizing the structural design of fiber. The proposed MRPCF is an all-solid-state fiber, which solves the instability problem of the magnetic fluid-filled fiber and reduces the complexity of the fabrication process. The all-solid-state MRPCF can be used in the development of quasi-distributed optical fiber magnetic field sensors and has broad applications in the fields of geological exploration, earthquake and tsunami monitoring, and military navigation.

Mid-infrared optical response to magnetic field in the La0.65Ba0.35MnO3 film grown by PLD

Optical and magneto-optical properties of the La0.65Ba0.35MnO3/SrTiO3(001) thin film with CMR and the paramagnetic-to-ferromagnetic transition at T = 310 K have been investigated in the infrared spectral range. It is shown that magnetotransmission and magnetoreflection of unpolarized light in the film reach up to 10 % at the magnetic field of 4kOe. The possible physical mechanisms responsible for negative magnetotransmission and positive magnetoreflection in the mid-infrared range are interpreted in the framework of the theory of magnetorefractive effect in manganites. High optical response of the La0.65Ba0.35MnO3 film to an external magnetic field (up to ∼ 25 %/kOe in the magnetoreflection) could be used in the design of optical magnetic field sensor, switches and modulators.

Design of photonic crystal fiber to excite surface plasmon resonance for highly sensitive magnetic field sensing.

To improve the sensing performance of optical fiber magnetic field sensor based on magneto-refractive effect, a D-shaped photonic crystal fiber-surface plasmon resonance (PCF-SPR) sensor based on magneto-refractive effect is proposed and its magnetic field sensing characteristics are investigated. The designed D-shaped PCF has a core-analyte-gold structure. Within the D-shaped PCF, the side polishing surface is coated with the gold film and the special hole is sandwiched between the core and the gold film. To realize the high magnetic field sensitivity for the fiber SPR magnetic field sensor, the special hole is filled with magnetic fluid (MF). In this paper, we analyze the mode transmission characteristics and magnetic field sensing characteristics of this fiber sensor by finite element method. We also obtain a general rule for the optimization of PCF-SPR sensors by analyzing the dispersion curves, the energy of the surface plasmon polariton mode and the core mode on the sensing performance of the designed fiber sensor. The maximum refractive index sensitivity and magnetic field sensitivity of the optimized fiber are 59714.3 nm/RIU and 21750 pm/mT (50-130 Oe), respectively. Compared with optical fiber magnetic field sensors based on magneto-refractive effect reported previously, the magnetic field sensitivity in this paper is nearly two orders of magnitude higher and it can initially achieve nT magnitude magnetic field resolution and testing capability. The proposed fiber sensor has the advantages of simple structure, easy production, high sensitivity, and strong environmental adaptability. It not only improves the sensing performance of optical fiber magnetic field sensors, but also provides an ideal alternative platform for biosensors like microfluidics because of its high refractive index sensitivity and the special structure.

Influence of particle size on the magneto-refractive effect in PbS quantum dots-doped liquid core fiber

In this study, magneto-refractive effects of PbS quantum dots (QDs)-doped liquid core fiber with different particle sizes were investigated. Based on the density function theory, the defect structures of PbS nanoclusters were constructed and the spin magnetic moments of sulfur (S) and plumbum (Pb) were analyzed. It indicates that the magnetic moments are mainly induced by the spin interaction between Pb 6s, 6p, and S 3p states, and the spin magnetism shows a weakening trend as the particle size increases. Based on the analysis, we experimentally studied the magneto-refractive effect with different sizes PbS QDs in liquid core fibers through a magneto-refractive index measuring system. The experimental results show that the magneto-refractive effect is strong as the size of PbS QDs decreases when the concentration is 8 mg/mL, exhibiting a maximum magneto-refractive sensitivity of -1.668×10−3 RIU/mT under the magnetic field of 0-7.89 mT, which can be used for magnetic field sensing applications.

Magneto-refractive properties and measurement of an erbium-doped fiber.

The magneto-refractive properties of an erbium-doped fiber (EDF) are investigated by theoretically analyzing the change in mode characteristics with a magnetic field and experimentally measuring it based on a fiber-optic Mach-Zehnder interferometer (MZI). The numerical results indicate that the mode effective refractive index (RI) increases as the magnetic field increases, and the mode field intensity distribution tends to be more concentrated in the core region with an increasing magnetic field. The variation in the mode effective RI of the fundamental mode with the magnetic field is greater than that of the higher-order modes. A magneto-refractive measurement system based on a fiber-optic MZI is set up to analyze the magneto-refractive effect of the EDF. The changes in the mode effective RI measured with a direct-current (DC) magnetic field and with a 100 Hz alternating-current (AC) magnetic field are 4.838×10-6 and 4.245×10-6 RIU/mT, respectively. The experimental results are in reasonable agreement with the theoretical analysis. Furthermore, the error between the experimental and numerical results is discussed. The magneto-refractive properties of the EDF exhibit potential in all-fiber magnetic field or current sensing area.

Giant magneto-refractive effect in mid-infrared second-harmonic generation from plasmonic antennas.

Active modulation of nonlinear-optical response from metallic nanostructures can be realized with an external magnetic field. We report a resonant 20% magneto-refractive modulation in second-harmonic generation (SHG) from spintronic multilayer antennas in the mid-infrared. We discuss mechanisms of this modulation and show that it cannot be explained by an unequal enhancement of the electromagnetic field. Instead, we propose a novel, to the best of our knowledge, contribution to the nonlinear susceptibility, which relies on the spin-dependent electron mean free path. In contrast to magneto-optics in ferromagnets, our approach allows simultaneous observation of the enhanced SHG and its large modulation.

Active photonic platforms for the mid-infrared to the THz regime using spintronic structures

Abstract Spintronics and Photonics constitute separately two disciplines of huge scientific and technological impact. Exploring their conceptual and practical overlap offers vast possibilities of research and a clear scope for the corresponding communities to merge and consider innovative ideas taking advantage of each other’s potentials. As an example, here we review the magnetic field modification of the optical response of photonic systems fabricated out of spintronic materials, or in which spintronic components are incorporated. This magnetic actuation is due to the Magneto Refractive Effect (MRE), which accounts for the change in the optical constants of a spintronic system due to the magnetic field induced modification of the electrical resistivity. Due to the direct implication of conduction electrons in this phenomenon, this change in the optical constants covers from the mid-infrared to the THz regime. After introducing the non-expert reader into the spintronic concepts relevant to this work, we then present the MRE exhibited by a variety of spintronic systems, and finally show the different applications of this property in the generation of active spintronic-photonic platforms.

Magnetoreflection and Kerr Effect in La2/3Ba1/3MnO3 Films with a Variant Structure

A correlation between the effect of magnetoreflection of natural light and tunnel magnetoresistance has been found in La2/3Ba1/3MnO3 films with a variant structure grown on ZrO2(Y2O3) substrates. It is shown that the magnetoreflection effect and giant magnetoresistance in these films are maximum in the region of magnetic ordering near room temperature (TC ≈ 295 K). Magnetoreflection spectra of a La2/3Ba1/3MnO3 film with a variant structure are formed via the same mechanisms as for films without a variant structure and can be described within the theory of the magnetorefractive effect. The field and temperature dependences of the magnetoreflection exhibit the presence of an additional low-temperature contribution to the reflection of a La2/3Ba1/3MnO3 film due to the tunneling of spin-polarized electrons through structural domain boundaries.

Магнитоотражение и эффект Керра в пленках La-=SUB=-2/3-=/SUB=-Ba-=SUB=-1/3-=/SUB=-MnO-=SUB=-3-=/SUB=- с вариантной структурой

A correlation was found between the magnetoreflection of natural light and tunneling magnetoresistance in La2 / 3Ba1 / 3MnO3 films with a variant structure grown on ZrO2 (Y2O3) substrates. It was shown that the magnetoreflection as well as the colossal magnetoresistance, is maximum in the region of magnetic ordering near room temperature (Tc ~ 295 K) of the films. The magnetoreflection spectra of a La2 / 3Ba1 / 3MnO3 film with the variant structure are formed by the same mechanisms as in the case of films without the variant structure and can be described in terms of the theory of the magnetorefractive effect. The field and temperature dependences of magnetoreflection demonstrate the presence of an additional low-temperature contribution to the reflection of the La2 / 3Ba1 / 3MnO3 film due to tunneling of spin-polarized electrons through the boundaries of structural domains.

Magnetooptical properties of epitaxial strained ferrite films grown by MOCVD method

CoFe2O4 (111) epitaxial films on a single crystalline (100) ZrO2(Y2O3) substrates and non-oriented CoFe2O4 films on a metal tape were grown by the metalloorganic chemical vapour deposition (MOCVD) method. The CoFe2O4/ZrO2(Y2O3) films contain the coherent high-angle boundaries between variant domains due to the complex epitaxial distortions compared to polycrystalline state of the CoFe2O4/(metal tape) film. The structural peculiarities of films with variant structure lead to the strong anisotropy of its magnetooptical properties. Moreover a significant magnetorefractive effect, up to 1 % at 6 kOe, is revealed in both the polycrystalline and epitaxial films with variant structure in the near infrared spectral range.

Features of Modeling of the Magnetorefractive Effect in Multilayered Metal Nanostructures

The magnetorefractive effect (MRE) is important and interesting from both fundamental and practical points of view. This effect consists in a change in the reflection coefficient or the passage of an electromagnetic wave from magnetized structures with magnetoresistance effects. It can be giant, tunnel and colossal magnetoresistance depending on the type of structure. MRE is most clearly manifested in the IR region of the spectrum and can reach tens of percent. It is possible to show its unambiguous dependence on the magnitude of the magnetoresistance. This article discusses the features of MRE in multilayer metal nanostructures with giant magnetoresistance. The MRE simulation is carried out using a model that relates this effect to magnetoresistance, as well as in the framework of the model taking into account spin-dependent scattering. The last model in earlier works allowed describing a number of experimental data well qualitatively and in some places quantitatively. In this paper, taking into account the frequency dependence of the resistance allowed us to improve the first model, which allowed us to obtain a good qualitative and quantitative description of the effect value – this is a fundamentally new result. The article highlighted the key opportunity for the application of magnetorefractive effect as a contactless method to study nanostructures, a method of nondestructive testing of all electronic components. A comparison with experimental data is also made. A good description is demonstrated in the framework of the two models considered, which can effectively describe the relationship between MRE and magnetoresistance.

Au dependence of the mid infrared optical and magnetorefractive properties of Ni81Fe19/Au GMR multilayers

We present an analysis of the optical and magnetorefractive properties of a series of Ni81Fe19/Au multilayers grown by magnetron sputtering as a function of the Au spacer thickness. The multilayers reach giant magneto resistance values of 4% with low magnetic fields for 2.3 nm Au spacers. The experimental results are well described taking only into account the contribution of the conduction electrons with spin dependent scattering times and different electron concentrations for the two spins. It is shown that the spectral response of the magnetorefractive effect depends strongly on the spin up vs. spin down ratio of both, scattering time and electron concentration. This dependence can be used to optimize mid infrared modulation of optical devices.

Magnetorefractive Effect in Multilayer Nanostructures

The relationship between the magnetorefractive effect (MRE) and giant magnetoresistance (GMR) is discussed. The common nature of these two effects in metallic multilayer magnetic structures is noted. The possibility of determining the parameters of the interface scattering of the conduction electrons through the analysis of the magnetoreflection of multilayer nanostructures in the intraband spectrum region is demonstrated. The underlying mechanisms of MRE and GMR are compared.

Features of Magnetorefractive Effect in a [CoFe/Cu] n Multilayer Metallic Nanostructure

The features of magnetorefractive effect (MRE) in metallic multilayer film Ni48Fe12Cr40(50 A)/[Co90Fe10(14 A)/Cu(22 A)]8/Cr(20 A) nanostructures, which exhibit giant magnetoresistance at room temperature, are investigated experimentally and theoretically. We show that the MRE in these structures reaches 1.5% in an applied magnetic field of 3.5 kOe, in a broad part of the IR region, and can change sign for both transmission and reflection of light. The refraction and extinction coefficients that are calculated for the nanostructures in an external magnetic field are in good agreement with our experimental data. The deduced formulas can be applied to estimating the MRE in multilayer metallic nanostructures.