Superconducting Quantum Interface Device Research Articles

Gravito-electromagnetic fields and superconductors in a regime of weak static gravitational field

A Deeper interweaving of different scientific areas has always proven to be a powerful tool for improving our understanding of several fascinating physical aspects of the world. For example, researchers worldwide have investigated the intriguing existence of the interaction between gravity and superconductivity in recent decades, owing to its enormous conceptual implications and various potential applications. Different theories using various approaches and techniques have been proposed to predict these interactions. To study the anomalous couplings between the super condensate and local gravitational field, we provide a detailed calculation of the thermodynamic properties and coherence length on behalf of the gravitational wave vector. In addition, this study provides a framework for calculating the gravitational penetration depth compared with the electromagnetic (E.M.) penetration depth. Furthermore, we demonstrate macroscopic quantum interference events by applying the Josephson effect using a superconducting quantum interface device (SQUID) link. Finally, similar to other calculations, we demonstrate how the quantum of the gravity flux is used to manage a sinusoidally oscillating current. This phenomenon will help future researchers study the effects of gravitational perturbation on supercurrents and super-condensates, and the latter could be used as ‘gravitational antennas’ for gravitational wave detection.

Coexistence of ferri and ferromagnetism in cobalt substituted samarium iron garnet

Samarium iron garnet (Sm3Fe5O12) is a potential but less explored ferromagnetic rare earth iron garnet. Cobalt substitution induced structural modifications that results enhancement in room temperature as well as low temperature magnetic behavior of Sm3Fe5O12 prepared by co-precipitation has been probed using superconducting quantum interface device. At room temperature, replacement of 0.3 atomic% Fe by Co improves the saturation value from 12.63 to 25.26 emu/g and the coercivity is found to be increased from 0.023 to 0.09 kOe. Similarly, at low temperature (∼5K) the enhancement in saturation magnetization and coercivity is found to be 17.62 to 31.23 emu/g and 1.55 to 2.32 kOe respectively. Rooted from the morphological modifications, the enhanced magnetism observed here might also be from the modifications in the super-exchange interaction and formation of oxygen vacancies due to the larger ionic radius of replaced Co2+ ions in the Fe3+ sites of Sm3Fe5O12.

CHARACTERIZATION AND STUDIES OF MAGNETIC PROPERTIES OF NANO-CRYSTALLINE NICKEL ZINC FERRITES (NiZn-Fe2O4) SYNTHESIZED BY CALCINATION METHOD

Nano crystalline form of nickel zinc ferrites (NiZn-Fe2O4) is prepared by high temperature calcination method at various proportion of Nickel and Zinc ions into the spinel structure of ferrites. The crystalline phase of as prepared NiZn-ferrites materials is characterized by XRD and TEM analysis. The magnetic properties of as prepared materials were analyzed by SQUID (superconducting quantum interface device) magnetometer. The broadening in XRD pattern due to nanoparticle formation in the crystalline phase of Ni-Zn-ferrites materials. TEM images are showing spherical and rectangular shapes of aggregated particle formation for Zn (0.6) Ni (0.4) Fe (2.0) )4 composition.

Investigation of steady state rheological properties and sedimentation of coated and pure carbonyl iron particles based magneto-rheological fluids

Abstract MR fluids face a major problem of sedimentation rate due to the high- density difference between the magnetic particles and the carrier medium that affects the performance of the magnetorheological devices. In this work, two MRF samples are prepared, where MRF-1 and MRF-2 are pure and coated carbonyl iron particles (CIPs) based MR fluids. The surface modification of the CIPs is performed using the solvent dispersion method to improve the sedimentation rate. The spherical shape and particle size analysis of the pure CIPs and coated CIPs’ morphology is investigated using the Scanning Electron Microscope (SEM). The Thermal Gravimetric Analysis (TGA) shows that the coated CIPs have high thermal stability and confirm that 6% by wt. coating is present in the coated sample. The chemical bonding of the coated CIPs is detected using the Fourier Transform Infrared Spectroscopy (FT-IR). The saturation magnetization (Ms) of pure and coated CIPs is 245 emu/g and 120 emu/g, respectively, at 15 kOe, which is obtained by using a superconducting quantum interface device (SQUID). The rheology flow curve properties show that MRF-1 and MRF-2 exhibit yield stress of about 10 kpa and 9 kpa, respectively, for varying magnetic fields ranging from 0 to 343 kA/m. The Herschel-Bulkley model is fitted with the experimental data and the shear thinning behaviour is observed for both MR fluids. The sedimentation study shows that MRF-2 has better settling rate than MRF-1, which is observed by using the visual observation method up to 600 h.

Development of zero boil-off cooling systems for superconducting self-shielded MEG

A mobile Magneto encephalography (MEG) of Sumitomo Heavy Industries, Ltd. (SHI) uses a high temperature superconducting magnetic shield (HTSMS), Superconductor-Normal-metal-Superconductor (SNS) type Superconducting Quantum Interface Device (SQUID) sensors, and they are cooled by a zero boil-off cooling system. The zero boil-off cooling system consists of a circulating cooled helium gas system for cooling the HTSMS below temperature 90 K and a helium recovery system for cooling the SNS type SQUID sensors to liquid helium temperature. The zero boil-off cooling system are designed to allow measurement in an operating state, allowing arbitrarily long usage. We succeeded first measurement of neuron current in brain by using SHI’s MEG with Helium zero-boil off cooling system at April, 2018. This paper describes overview of SHI’s MEG, the thermal design of the zero boil-off cooling system for our MEG and the results of cooling tests.

Nanocrystalline cobalt hydroxide oxide: Synthesis and characterization with SQUID, XPS, and NEXAFS

Nanocrystalline cobalt hydroxide oxide (nc-CoOOH) particles were synthesized via a precipitation-oxidation mechanism with different oxidation agents. Since the choice of the oxidative compound is of great practical importance, we compared the properties of the nc-CoOOH particles obtained from the oxidation with O2 and Br2. The particles from both synthesis routes were fully characterized with X-ray powder diffraction (XRPD), infrared spectroscopy (IR), superconducting quantum interface device (SQUID) measurements, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) measurements. It was found that the choice of the oxidation agent greatly affects the properties of the resulting nanoparticles; the most significant differences concern particle size and magnetic moment, due to residual Co2+. Although both, Br2 and O2, lead to the formation of nc-CoOOH, particles obtained from the synthesis involving O2 show a three times larger particle size than their counterparts obtained from the synthesis using Br2 (24 nm vs. 8 nm). Furthermore, using Br2 during the synthesis leads to an 8-fold increase of the amount of residual Co2+ impurities, which, in fact, induce a magnetic moment. A possible enrichment of those Co2+ impurities on the surface of the nanoparticles is discussed based on XPS and NEXAFS data.

Fabrication of Au/Ni/NiO heterostructure nanowires by electrochemical deposition and their temperature dependent magnetic properties

Magnetic heterostructure nanowires with three different compositions (i.e. Au–NiO–Au, Ni–NiO–Ni, and Au–Ni–NiO) were successfully fabricated via simple chronoamperometric technique of the electrochemical deposition. Morphologies and compositions of the prepared samples were analyzed by the field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD), respectively. Magnetic properties of the fabricated nanowires were measured with the help of superconducting quantum interface device (SQUID) in a temperature range (2 ​K–300 ​K). The temperature dependent magnetic properties indicate that the heterostructure nanowires are composed of the superposition of ferromagnetic, anti-ferromagnetic components and exhibiting superparamagnetism and spin-glass like behaviors in different temperature range. Low temperature magnetization reveals high anisotropy of the prepared samples and showing high magnetization at the Ni/NiO interface of the nanowires. These nanostructures might have potential applications in the memory devices.

Magnetic properties of nanocrystalline nickel incorporated CuO thin films

Abstract CuO films were deposited on fused silica substrates by using sol-gel method. Nanocrystalline nickel was incorporated in CuO in varying concentrations to form Ni:CuO films. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and Raman spectroscopy measurements were carried out to characterize the films. X-ray photoelectron spectroscopy (XPS) studies indicated that Ni ions successfully substituted Cu in the CuO lattice. Superconducting quantum interface device (SQUID) measurements were carried out to measure the magnetization of the films which decreased with increase in temperature. Coercive field and residual magnetization in the Ni:CuO films were measured as a function of nickel content in the CuO films.

In-situ magnetic force microscopy analysis of magnetization and demagnetization behavior in Al3+ substituted Sr-hexaferrite

The sintering temperature of an Al3+ substituted Sr-hexaferrite composite was systematically varied from 1180 °C to 1280 °C resulting in different microstructures. The grain size was found to range from a few hundred nanometers to several hundred micrometers depending on Al content and sintering temperature. Adding an Al substituted powder to a commercial powder increased the coercivity from 360 mT to 470 mT, at the same time, decreasing remanence from 350 mT to 305 mT. Magnetization and demagnetization processes from the thermally demagnetized state (TDS) and DC-demagnetized state (DCD) have been investigated systematically by in-situ magnetic force microscopy (MFM) under magnetic field. From the surface domain contrast a polarization was derived which quantitatively matches the global i.e. bulk polarization obtained by superconducting quantum interface device (SQUID) magnetometry. The shape of the initial polarization curve and the polarization from the DCD state were correlated with the in-situ MFM data revealing a distinctly different magnetization behavior depending on grain size. The presented results enable a better understanding of local nucleation mechanisms, global influences of pinning centers and further opportunities to improve rare earth (RE) free permanent magnets based on ferrites.

Structural, magnetic, elastic, dielectric and electrical properties of hot-press sintered Co1−xZnxFe2O4 (x = 0.0, 0.5) spinel ferrite nanoparticles

In this article, Co1−xZnxFe2O4 (x=0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925°C for 10min in vacuum atmosphere under 30MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co1−xZnxFe2O4 (x=0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co1−xZnxFe2O4 (x=0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47emu/g was obtained for Co0.5Zn0.5Fe2O4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (Vl), transverse wave velocity (Vt), mean elastic wave velocity (Vm), bulk modulus (B), rigidity modulus (G), Young’s modulus (E), Poisson ratio (σ) and Debye temperature (θD) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model.

Effect of Zn Doping on Structural and Magnetic Properties of Ba4Ni2−x Zn x Fe36O60 Hexaferrites

Polycrystalline Ba4Ni2−xZnxFe36O60 (0.0 ≤ x ≤ 1.4) hexagonal ferrite samples have been prepared by conventional solid-state reaction method. Structural and magnetic properties of the prepared samples were then ana- lyzed by the X-ray diffraction technique and with supercon- ducting quantum interface device (SQUID) magnetometer, respectively. Variations of lattice parameters, density, and porosity with Zn content were measured. Magnetic prop- erties such as complex permeability, relative quality factor, loss factor, and saturation magnetization have been investi- gated as a function of Zn content. The study revealed that Zn content has a significant effect on structural and magnetic properties of the Ba4Ni2Fe36O60 hexaferrites.

Ferromagnetic behavior of nanocrystalline Cu–Mn alloy prepared by ball milling

50Cu–50Mn (wt%) alloy was produced by ball milling. The milling was continued up to 30h followed by isothermal annealing over a four interval of temperature from 350 to 650°C held for 1h. Crystallite size, lattice strain, lattice parameter were determined by Rietveld refinement structure analysis of X-ray diffraction data. The amount of dissolved/precipitated Mn (wt%) after ball milling/milling followed by annealing was calculated by quantative phase analysis (QPA). The increase of coercivity could be attributed to the introduction of lattice strain and reduction of crystallite size as a function of milling time. Electron paramagnetic resonance and superconducting quantum interface device analysis indicate that soft ferromagnetic behavior has been achieved by ball milled and annealed Cu–Mn alloy. The maximum coercivity value of Cu–Mn alloy obtained after annealing at 350°C for 1h is 277Oe.

NMR investigation of functionalized magnetic nanoparticles Fe3O4 as T1–T2 contrast agents

In this paper, we report the synthesis of size-controlled (6 and 18nm) monodisperse magnetic iron oxide nanoparticles, from the pyrolysis of iron oxyhydroxide with oleic acid in high temperature solvents. Superconducting Quantum Interface Device (SQUID) measurements revealed that the iron oxide nanoparticles exhibit a superparamagnetic behavior at room temperature. In order to evaluate their potential applications as contrast agents in Nuclear Magnetic Resonance (NMR) imaging, we investigated using 1H NMR spectroscopy (at a magnetic field 4.7T) the changes in T1 and T2 relaxation times in the colloidal aqueous solution at various concentration of nanoparticles. The following transverse (r2) and longitudinal (r1) relaxivities were found: (r2=17.85mM−1s−1, r1=6.90mM−1s−1) and (r2=9.20mM−1s−1, r1=4.30mM−1s−1) for nanoparticle sizes of 18 and 6nm, respectively. These results confirm that the synthesized nanoparticles have both high r1 and r2 relaxivities and thus the capacity for positive or negative contrast enhancement. This effect increases with the nanoparticle size. We also developed a new recognition motif of a saccharide type (mannose coating) for targeting biological models (plants) at the tissue and cellular levels in order to track the flow of the water and saccharide (which are the main drivers of plant growth) in NMR imaging. Moreover, we demonstrated that this saccharide motif provides good biocompatibility and biodistribution in a physiological medium.

Surface functionalized LSMO nanoparticles with improved colloidal stability for hyperthermia applications

LSMO (La0.7Sr0.3MnO3) magnetic nanoparticles (MNPs) coated with double layer oleic acid (OA) surfactant are prepared to make a water based magnetic nanofluid for hyperthermia application. Various experimental techniques are used for bilayer coating analysis. The effect of the bilayer coating on magnetic properties is studied by superconducting quantum interface device (SQUID). Colloidal behaviour of coated MNPs in aqueous medium is studied by the zeta potential and dynamic light scattering. The effects of pH and ionic strength on the colloidal stability of the MNPs are studied in detail. For the bilayer-coated LSMO MNPs aggregation is not observed even in high ionic strength and at physiological pH (7.4). For making the nanofluid of the bilayer-coated MNPs the colloidal stability is studied in physiological media like phosphate buffer solution. Under induction heating experiment, hyperthermia temperature (42–43 °C) could be achieved by the bilayer-coated sample at a magnetic field of 168–335 Oe and frequency of 267 kHz. The bilayer OA coating can hinder the agglomeration of MNPs significantly and produce stable suspension with improved hyperthermia properties. The bilayer OA coating also improves the specific absorption rate (SAR) of LSMO MNPs from 25 to 40 W g−1.

Magnetic behaviour of Ni0.4Zn0.6Co0.1Fe1.9O4 spinel nano-ferrite

Nanoparticles of the spinel ferrite Ni0.4Zn0.6Co0.1Fe1.9O4, have been synthesized by a co-precipitation method. The x-ray diffraction patterns of the particles confirmed the formation of single-phase cubic spinel structure. The Langevin function fitting on M-H data at 300 K gives a log-normal particle size distribution with median diameter of 59.6 nm and standard deviation of 0.6. The isothermal dc magnetization studies have been performed using the superconducting quantum interface device and vibrating sample magnetometer in the temperature range of 5-300 K. These measurements show that the sample is superparamagnetic above the blocking temperature TB ∼ 253 K when an external magnetic field of 20 Oe is applied. The reduction in saturation magnetization in case of nanoparticles may be attributed to the fact that magnetic moments in the surface layers outside the core are in the state of frozen disorder. A doublet observed in the Mössbauer study also confirms the superparamagnetic behavior and nanocrystalline formation.

Characteristic Analysis of Directly Coupled HTS dc-SQUID Magnetometer With Superconducting Film Magnetic-Shield Considering Josephson-Junction Resistance

A high temperature superconducting quantum interface device (HTS SQUID) is an extremely sensitive magnetic sensor. The HTS SQUID is required to have a high robustness with respect to magnetic noise for stable operation outside a magnetic shielding room. In order to achieve the high robustness of HTS SQUID, use of a magnetic shield with a superconducting film has been proposed, and its effectiveness has been confirmed in the experiments. In this paper, an electromagnetic field simulation was performed using the 3-D edge finite element method to confirm the effectiveness of the superconducting film magnetic-shield. Since both the SQUID magnetometer and the superconducting film magnetic-shield are made of HTS, it is required to consider the HTS characteristics in the electromagnetic field simulation. Additionally, the SQUID magnetometer has Josephson junction. In this paper, the property of the Josephson junction is also considered. The simulation accuracy depending on the type of the finite element mesh is also investigated.

Detection of brain auditory evoked magnetic field based on low-Tc superconducting quantum interface device

Superconducting quantum interface devices (SQUID) is widely used in human brain signal detection. As one of the applications of magnetoencephalography (MEG) system, the detection of the auditory evoked response is useful for the development of MEG system and the research into auditory mechanism of human brain. Generally, the auditory evoked response includes three peaks which are P50m, N100m and P200m. We develop a single-channel MEG system in a magnetically shielded room based on the superconducting quantum interface device (SQUID) and second-order axial gradiometer. The responses of the main peak N100m under different tone frequencies are preliminarily studied by using our system. The typical evoked response of N100m to 1 kHz pure tone and 100 ms duration is measured to be 0.4 pT. Under the tone stimulus at low frequency, the delay of the peak N100m to the tone onset is 125 ms at 100 Hz, which is longer than the typical value of 100 ms. In comparison with the response to 1 kHz pure tone stimulus, the amplitude of the evoked response in a random frequency range from 1 kHz to 4 kHz is stronger and the delay is several milliseconds. This work lays the foundation of the studies of the auditory mechanism and multichannel MEG system by using software gradiometers.

Investigations of cobalt and carbon codoping in gallium nitride for spintronic applications

Extensive theoretical investigations have been carried out to study the ferromagnetic properties of transition metal doped wurtzite GaN using the Tight Binding Linear Muffin-tin Orbital (TBLMTO) method within the density functional theory. The present calculation reveals ferromagnetism in cobalt doped GaN when one gallium is replaced by cobalt in a 3×3×2 supercell of GaN, which gives rise to a cobalt concentration of 2.77%. The system is half-metallic with a magnetic moment of 4.0μB. When Co is bonded with one carbon, there is a drastic decrease in magnetic moment and the system becomes metallic. When Co dimer is introduced via nitrogen which corresponds to the Co concentration of 5.5% the magnetic moment is 3.99μB and the system is half-metallic. Same trend is observed when Co is bonded via nitrogen with unequal distance. When cobalt dimer is formed via carbon, the moment becomes 2.95μB and it shows metallic character. For dimer via carbon with unequal distance, the moment is 3.0μB and the system becomes semiconductor. For higher percentage of cobalt dopant the system shows metallic character. C and Co doped GaN samples have been synthesized experimentally and characterized with X-ray diffraction, transmission electron microscopy, micro-Raman and superconducting quantum interface device measurements. The observed results are correlated with the theoretical studies.

Synthesis and Characterization of Nanocrystalline Zinc Manganese Ferrite

Zn x Mn 1―x Fe 2 O 4 is a prototypical soft magnetic material, and commonly used for high-frequency applications due to its low power loss and high permeability and resistivity. Various wet chemistry routes have been developed for synthesizing Zn x Mn 1―x Fe 2 O 4 ; however, multistep procedures are usually involved in these methods, making them complex in implementation. Here, we use a facile chelate method to prepare Zn x Mn 1―x Fe 2 O 4 sol precursor for fabricating both fine powders and nanocrystalline thin films. X-ray diffraction and electron microscopy techniques are used to characterize the microstructure and composition of as-synthesized Zn x Mn 1―x Fe 2 O 4 , and superconducting quantum interface device is used to measure their magnetic properties. The investigation of powders with different Zn/Mn cation concentration indicates that the saturation magnetization is determined by the content parameter x; while the coercive field is closely correlated to the crystal size. Further, Zn 0.4 Mn 0.6 Fe 2 O 4 thin films were deposited using spin-coating technique, and annealed at different temperatures to study the formation of the impurity phase.

Investigations on cobalt doped GaN for spintronic applications

(Ga1−xCox)N was synthesized at 1223K using pure gallium and cobalt metal as precursors in a reactor specially designed for this purpose with ammonia as the nitrogen source. The structural confirmation of wurtzite phase of GaN is done using powder X-ray diffractometer. Photoluminescence shows red shift in band edge emission as the cobalt concentration increases from 1 to 5 atomic percentage together with nitrogen related vacancy emission at 3.24eV and cobalt related emission at 3.13eV. The magnetic properties were studied at 10K using superconducting quantum interface device (SQUID). The obtained maximum magnetic moments for 1%, 3% and 5% cobalt doped GaN are 1.63, 0.21 and 0.14μB, respectively. The decrease in magnetic moment with increase in dopant concentration may be due to the formation of secondary phases or cobalt cluster, which contributes to anti-ferromagnetism. From temperature dependent magnetization measurements it is observed that there is no drastic change in the magnetic moment upto room temperature for 1% cobalt doped GaN. Theoretical calculations based on the density functional theory within Tight Binding Linear Muffin-tin Orbital (TBLMTO) method has been carried out to study the magnetic properties of cobalt doped GaN. The obtained magnetic moment values per Co atom are 2.56μB for 1.56% and 2.77% and 1.50μB for 4.20%. This is found to be higher when compared with experimental values and this difference is explained based on structural defects and percentage of dopant used during synthesis. The half metallic behavior is observed for 1.56% and 2.77% Co dopants, but for higher percentage of dopant the system becomes metallic. Hence, it is concluded that only lower percentage of cobalt doped GaN is suitable for spintronic applications.