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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Superconductor Electronics: Status and Outlook

Superconductor electronics combines passive and active superconducting components and sometimes normal resistors into functional circuits and systems that also include room-temperature electronics for amplification, power sources, necessary controls, etc., usually computer operated. Furthermore, complete systems include magnetic and electromagnetic shielding, cryogenic enclosures, and increasingly a cryocooler in self-contained units. Components or devices of low or high critical temperature superconductors include inductances (coils), passive transmission lines, resonators, antennae, filters, as well as active elements: Josephson junctions, Josephson oscillators, and superconducting quantum interference devices. Of multiple demonstrated applications, mostly but not only in science and metrology, currently most successful are voltage standards, astronomy detectors and large telescope cameras, instruments for material characterization, and magnetometers for geomagnetic prospecting. Major current efforts concentrate on energy-efficient high-end computing and quantum computing. The outcomes of these efforts are likely to be known in the course of the following decade.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of Zn, Ga and Gd Doping on Structural and Magnetic Properties of Nanonickel Ferrite Prepared by Two Different Methods

Zn/Ga/Gd-substituted NiFe{sub 2}O{sub 4} was formed by solid state reaction and citrate methods. The influence of substitutions on phase formation, the strain, crystallize size, cations distribution and magnetic properties have been examined by X-ray diffraction, Mössbauer effect spectrometer, Fourier-transform infrared, and vibrating sample magnetometer. Zn/Ga/Gd substituted NiFe{sub 2}O{sub 4} samples prepared by solid state method showed that as gadolinium introduced into the system, a second phase was formed with a small percentage while samples prepared by citrate method exhibited a single phase. The distributions of different cations between different sites were determined by both Mössbauer effect spectroscopy, modified Bertaut and Rietveld analysis. Mössbauer technique at room temperature showed that samples synthesized by the ceramic method have a magnetic order while samples prepared by citrate method have a superparamagnetic nature. The canting angle between magnetic ions was increased by increased the amount of Zn in samples prepared by both methods.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effects of Nd, Al Doping on the Structure and Properties of BiFeO{sub 3}

The BiFeO{sub 3}(BFO) and Bi{sub 0.95}Nd{sub 0.05}Fe{sub 1-x}Al{sub x}O{sub 3} (x = 0, 0.03, 0.05, 0.075, 0.1) powders were prepared at 200 °C for 24 h by hydrothermal method. The effects of Al doping content on the structure, morphology, magnetic, and photocatalytic properties were studied. X-ray diffraction (XRD) and Fourier transform infrared spectrometer (FTIR) demonstrated the compounds are distorted rhombohedral perovskite structure without any other heterogeneity and structural transition. Field emission scanning electron microscope (FESEM) reflected surface of compounds is a dense, agglomerated sphere. As the concentration of Al{sup 3+} increases, a small part of the spherical crystallites eventually becomes cauliflower shape. Energy-dispersive X-ray (EDS) showed the Bi{sub 0.95}Nd{sub 0.05}Fe{sub 0.95}Al{sub 0.05}O{sub 3} sample mainly consists of five elements (Bi, Fe, O, Nd, Al) and atom radio matched well with the formula. Vibrating sample magnetometer (VSM) integrated in a physical property measurement system (PPMS-9) illustrated introducing Nd{sup 3+} ions into BFO will enhance its magnetism at room temperature. However, with the increase of non-magnetic ion Al{sup 3+} concentration in Bi{sub 0.95}Nd{sub 0.05}Fe{sub 1-x}Al{sub x}O{sub 3} (x = 0, 0.03, 0.05, 0.075, 0.1), the network structure of Fe-O-Fe was destroyed, which led to the decrease of its net magnetization, so that the hysteresis loop shows paramagnetism. The photocatalytic performance of BFO increased initially and decreased afterwards as Al{sup 3+} concentration increased, and the best catalytic performance was achieved at x = 0.05.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Characterization of Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3}@ SiO{sub 2} Core-Shell Structure Composite Magnetic Fluid by Microemulsion Method

Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3}@SiO{sub 2} composite magnetic fluids were prepared successfully by microemulsion method in this study. Fe{sub 3}O{sub 4} magnetic nanoparticles (Nps) were successfully converted to Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3} magnetic Nps by low-temperature low-vacuum oxidation method (LTLV oxidation method), and then coated with silica by the modified Stöber method. The core-shell structure composite magnetic Nps were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and transmission electron microscopy (TEM). The results show that the size of Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3} particles was about 13 nm and that of SiO{sub 2} coating was about 3 nm, and the saturation magnetization of Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3}@SiO{sub 2} Nps was 59.12 A m{sup 2}/kg and 35.84 A m{sup 2}/kg, respectively. And the saturation magnetization of Fe{sub 3}O{sub 4}/γ-Fe{sub 2}O{sub 3}@SiO{sub 2} magnetic fluid was 22.91 A m{sup 2}/kg.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Investigation of Magnetic and Microwave Absorption Properties of Ba{sub (1−2x)}La{sub x}Na{sub x}Fe{sub 10}CoTiO{sub 19} Hexaferrites in 18.0–26.5 GHz Band

A series of Ba{sub (1−2x)}La{sub x}Na{sub x}Fe{sub 10}CoTiO{sub 19} hexaferrite samples with x = 0.00–0.25 (step size 0.05) were prepared by using conventional solid-state reaction technique. The magnetic properties of the hexaferrites have been investigated at room temperature by employing a vibrating sample magnetometer. There is an overall decrease in saturation magnetization from 70.64 to 57.83 emu/g with an increase in doping concentration from x = 0.00–0.25. The microwave measurements were done utilizing vector network analyzer in the k-band (18.0–26.5 GHz) frequency range. The electromagnetic measurements revealed that the gross tangent loss is maximum for x = 0.10 sample. The microwave absorption measurements show that sample x = 0.10 with 1.4 mm thickness exhibits a reflection loss of − 26.59 dB (99.78% signal absorption) and 7.65 GHz bandwidth. Thus, it is considered for thin single-layer broadband microwave absorber applications in 18.0–26.5 GHz frequency range.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Superparamagnetic Properties and Significant Applications of Iron Oxide Nanoparticles for Astonishing Efficacy—a Review

This paper reviewed the comprehensive literature survey on the physical, chemical, and the catalytic properties and applications of iron oxide nanoparticles. In recent years, iron oxide has made a versatile progress due to its outstanding magnetic property. The average crystallite size was reported in previous literatures in the range of 10–45 nm using Scherrer’s formula. The powder morphology was found to deliberate quasi-spherical and predominantly spherical shape. The specific surface area as measured by N{sub 2} adsorption BET isotherm was reported in the range of 17.6–26.21 m{sup 2}/g. Depending on the synthesis pathway there was, an inverse or normal spinel structure could be achieved. X-ray diffraction analysis revealed the crystallite size in the range between 8 and 42 nm. Fourier transform infrared spectroscopy reported the changes in functional group, stretching vibrations in the iron oxide nanoparticles. Scanning electron microscopy analysis showed most of Fe{sub 3}O{sub 4} nanoparticles were in spherical morphology with the particle size range between 10 and 26 nm. Vibrating sample magnetometer reported the magnetization value for Fe{sub 3}O{sub 4} nanoparticles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Correlation Between Magnetization and Particle Size of CdS Nanostructures by Solvothermal Method

Micro- and nano-structures of CdS including microrods, nanoparticles, nanorods, microspheres, and nanosheets were prepared by solvothermal method using monoethanolamine (EA), ethylene glycol (EG), and ethylenediamine (EN) to act as a mixed and pure solvent at multiple Cd and S concentrations. X-ray diffraction (XRD) patterns have shown CdS micro- and nano-structures with hexagonal and wurtzite structures. Scanning electron microscopy (SEM) has depicted nanosheet existence, microsphere, and microrods of CdS at various volume ratios. Transmission electron microscopy (TEM) has shown nanorod existence and nanoparticles of CdS at various volume ratios. Optical properties have been investigated using UV-Vis. A vibrating sample magnetometer (VSM) has been used to measure the CdS nanoparticle ferromagnetism at ambient temperature. The saturation magnetization has exhibited 9.109 (10{sup −3} emu/g). The ferromagnetic properties of CdS are referred to their structural defects.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Zn Concentration on the Structure, Morphology, and Magnetic Behavior of Ni{sub 1 − x}Zn{sub x}Fe{sub 2}O{sub 4} Ferrofluid

In this work, we investigated the effect of doping zinc ions onto nickel ferrite upon the structure, morphology, and magnetic properties of Ni{sub 1 − x}Zn{sub x}Fe{sub 2}O{sub 4} ferrite nanoparticles (x = 0, 0.25, and 0.75) prepared via co-precipitation method. X-ray diffraction analysis showed the presence of the most intense peak corresponding to the (311) crystallographic orientation of NiFe{sub 2}O{sub 4} cubic spinel phase, and the crystallite size obtained from Scherrer formula increased from 6.8 to 11.2 nm when the Zn concentration increases from x = 0 to x = 0.75. Fourier transform infrared spectroscopy analysis confirmed the presence of a prominent band associated to the vibrations of metal ions, as a feature of spinel ferrite phase formation, observing that their band positions were very sensitive to Zn doping concentration. Transmission electron microscopy studies allowed to determinate that for all Zn concentrations, the particle sizes are around 15 nm. The magnetic properties were studied by using the vibrating sample magnetometer at room temperature. The results reveal superparamagnetic behavior determined by the shape of the hysteresis loop, presenting decreased coercive magnetic field and increased saturation magnetization, with increased zinc concentration. Additionally, from field cooling and zero field cooling curves, we can observe the typical behavior of the blocking process assembly of superparamagnetic nanoparticles. Alternate current susceptibility measurements show that the blocking temperature is frequency dependent and shifts toward higher temperatures by increasing the frequency, a characteristic of superparamagnetic, and glassy systems. Furthermore, τ{sub 0}, related to the jump attempt frequency of the magnetic moment of the nanoparticle between the opposite directions of the magnetization easy axis, is in the range of 2 × 10{sup −10} and 7 × 10{sup −13} s for the three different Zn concentrations, which agrees with characteristic of non-interacting superparamagnetic systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Substrate Temperature on Structural, Morphological, Magnetic, and Electrical Properties of Fe{sub 2}CoSi Heusler Alloy Thin Films for Spin-Based Device Applications

Fe{sub 2}CoSi based Heusler alloy thin films are deposited on single crystal Si (111) substrate at different substrate temperatures varying from room temperature to 600 °C using ultrahigh vacuum DC magnetron sputtering. Structural analysis of the prepared thin films is carried out using GI-XRD measurement and it conform ordered L2{sub 1} crystal structure of the films deposited at 450 °C and above. The atomic force microscopic (AFM) images of Fe{sub 2}CoSi thin films exhibiting 3D-like growth on Si (111) substrate at varying temperatures. The magnetic property of the thin films is studied using vibrating sample magnetometer (VSM). At 450 °C of substrate temperature, the prepared thin film exhibits high saturation magnetization (M{sub s} = 948 emu/cc) and low coercivity (H{sub c} = 8 Oe). The self-energy magnetization of the film and its own field is very high, when the temperature of the substrate was maintained at 450 °C and switching field ratio for this film was obtained as ~ 0.9 due to its high crystallinity and atomic ordering. The electrical property of Fe{sub 2}CoSi thin film is investigated using four-probe technique and a positive magnetoresistive behavior was observed for thin film deposited at a substrate temperature of 450 °C which indicates the possible half-metallic nature at room temperature. The enhanced magnetic and electrical properties obtained for the thin film prepared at 450 °C substrate temperature is highly suitable for spin based device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Electrochemical Investigations of Magnetic Co{sub 3}O{sub 4} Nanoparticles as an Active Electrode for Supercapacitor Applications

This attempt reports on cobalt oxide (Co{sub 3}O{sub 4}) nanoparticles (NPs) prepared through the traditional chemical reflux method to examine the behavior of supercapacitor performance. The synthesized NPs were characterized using several analytical tools such as ultraviolet-visible spectroscopy (UV), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) pattern, and scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX). Moreover, the electrochemical performance was analyzed using galvanostatic charge and discharge studies (GCD), cyclic voltammetry (CV) studies as well as electrochemical impedance spectroscopy (EIS). The cubical phase of Co{sub 3}O{sub 4} was identified from the XRD pattern and also the average crystalline size was measured by Scherrer’s equation. FTIR confirmed the functional group of Co{sub 3}O{sub 4} NPs. SEM images revealed the hexagonal-shaped nanoflakes-like morphology of the sample. From the elemental analysis, the formation of pure Co{sub 3}O{sub 4} NPs by means of high purity and composition ratio of cobalt with oxygen was found. Vibrating sample magnetometer (VSM) plot scrutinized the magnetic performance of Co{sub 3}O{sub 4} NPs{sub .} The Co{sub 3}O{sub 4} NPs modified electrode has delivered maximum specific capacitance as 1413 Fg{sup −1} at a current density of 1 Ag{sup −1} which maintains tremendous cycling stability within the retention ratio of 98.4% after 1000 cycles. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Characterizations of Binary FeCr (AISI 430) Thin Films Deposited from a Single Magnetron Sputtering Under Easy Controllable Deposition Parameters

A series of 50-nm binary FeCr martensitic thin films were sputtered from a single source made of commercial AISI 430 ferritic stainless steel under the deposition rates gradually increased from 0.03 to 0.11 nm/s with 0.02 nm/s steps at stationary condition. And, under 0.09 nm/s deposition rate, a second series of the films were also deposited under the rotation speed of their substrates which was chosen at 0, 25, and 45 rpm. As far as we are concerned, this study is the first investigation of properties of the thin films produced from AISI 430. The atomic Fe content in the films increased from 79.3 to 98.6% while atomic Cr content decreased from 20.5 to 1.2% with the increase of deposition rate from 0.03 to 0.11 nm/s. According to compositional analysis, the Fe content increased while Cr content decreased with increasing deposition rate. The reason for this may be attributed to the relatively different bond energy/melting point of metals which have different contents sputtered from source material since this physical parameter is very significant for the sputtering process. And, the Fe content in the films decreased from 84.9 to 79.2 at. % while the Cr content increased from 14.9 to 20.6 at. % when the increase of rotation speed of substrate. The crystal structure of all films was observed to have a body-centered tetragonal phase and the intensity of (110) peak varied with the atomic Fe content. The surface observations of films performed by a scanning electron microscope exposed that the number of surface grains increased with the increase of deposition rate and decreased with the increase of rotation speed. According to surface roughness analysis done by an atomic force microscope, the roughness of the film surfaces increased as the deposition rate increased. And, the roughness of the film surfaces decreased as the rotation speed increased. This has been consistent with the grain size and roughness parameters. Thus, increasing deposition rate and decreasing rotation speed of the substrate caused an increase in grain size and roughness parameters. The magnetic measurements of the films achieved, by a vibrating sample magnetometer at room temperature, displayed that the saturation magnetization, M{sub s}, values increased from 820.1 to 1700.4 emu/cm{sup 3}, the remanence magnetization, M{sub r}, values increased from 293 to 817 emu/cm{sup 3}, and the coercivity, H{sub c}, value also increased from 38 to 107 Oe with the increasing of deposition rate. It is also seen that the magnetic easy axis are in the film plane due to the shape anisotropy. With the increase rotation speed, the values of M{sub s} and M{sub r} increased and the H{sub c} decreased. It was seen that variation of Fe content in the films influences the M{sub s} values and the H{sub c} values are consistent with the surface properties. It was concluded that the deposition rate and the rotation speed of the substrate play a considerable role on the structural and related magnetic properties of the sputtered FeCr thin films, and the properties of the films can be easily controlled by changing production parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Benchmark Analysis on Magnetic and Photoluminescence Properties of Selective Metal Ions Doped ZnS Nanoparticles

The creation of diluted magnetic semiconductors (DMSs) at lower dimensions that exhibit room temperature ferromagnetism (RTFM) has been given immense significance for the fabrication of a new class of spintronic devices through utilizing spin degrees of freedom besides charge nature of electrons. In this view, nanocrystals of ZnS doped with 4% concentration of Fe, Co, Ni, Cr, Mn, Sr, Cu, and Ce have been synthesized at room temperature (RT) by chemical co-precipitation method. The samples were examined by various characterization techniques like energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and photoluminescence (PL). EDS spectra revealed the existence of parent elements in the prepared samples. XRD characterization disclosed hexagonal structures of nanocrystals, and no secondary phases were observed in all the samples except for Cu and Ni doped ZnS. FTIR data confirmed the proper substitution of dopants in the host lattice as all the graphs have almost same stretchings. The magnetic nature of each sample was evaluated from M-H graphs of VSM, and it corroborated the transition of magnetic properties due to doping. Pristine ZnS showed diamagnetic nature, while Fe and Sr doped ZnS evinced strong ferromagnetic and anti-ferromagnetic properties, respectively. Photoluminescence studies on Ce, Sr and Mn doped ZnS samples revealed strong emission peaks with enhanced luminescence properties compared to bare ZnS. Cu, Cr and Mn doped ZnS exhibited a red shift in emission wavelengths, whereas Co doped ZnS showed emission peak shifted towards the blue region as compared to the host lattice.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Structural and Magnetic Behavior of BaAl{sub x}Cr{sub y}Fe{sub 11}O{sub 19} (x + y = 1) Hexagonal Ferrites

The present study aims to analyze barium hexagonal ferrite and its derivation behavior using sol-gel auto-combustion co-doped with Al{sup 3+}/Cr{sup 3+}ions. Also, the effects of dopants on structural and magnetic properties of prepared samples were investigated. To this purpose, the finest powders were preheated at 500 °C for 1 h and calcinated at 900 °C about 2 h. Then, the magnetic powders were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and vibrating sample magnetometer (VSM). The XRD patterns show the magnetoplumbite phase. According to the Scherrer equation applied, inserting ions led to a decrease in lattice parameters (a and c) and crystallite size. The morphology of synthesized samples was observed by FESEM and proved the hexagonal shapes of the prepared samples. The nanoparticles sizes were recorded between 59 and 79 nm. Moreover, the magnetic properties of prepared samples were specified by VSM. The saturation magnetization (M{sub s}) and remnant magnetization (M{sub r}) of the synthesized magnetic powders were decreased by inserting Al{sup 3+}/Cr{sup 3+} ions, while coercivity (H{sub c}) increased from 5215 to 7178 Oe. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Electrical, Structural, and Thermal Properties of Ferrite/Superconductor (Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}){sub x}/YBa{sub 2}Cu{sub 3}O{sub 7-δ}) Nanocomposite Materials

The superconductor YBa{sub 2}Cu{sub 3}O{sub 7-δ} (Y123) is prepared by the solid-state route, while the nanosized Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (Ni-Zn ferrite) is synthesized via citric acid sol-gel technique. The composite material of the type (Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}){sub x}/YBa{sub 2}Cu{sub 3}O{sub 7-δ}, where x = 0.00, 0.03, 0.10, and 0.50 wt%, is prepared by a modified solid-state method to study the effect of doping Ni-Zn nanosized ferrite on the superconducting, structure, and thermal properties of Y123. The prepared samples show Meissner effect which confirmed the presence of superconducting phase at liquid nitrogen temperature (77 K). The prepared samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion of X-ray (EDX), infra-red (IR) spectroscopy, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), DC resistance by four-probe, and critical current density measurements. It was found that by increasing Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles in the Y123 compound, the unit cell volume of the orthorhombic phase decreases, but the transition temperature T{sub c} and critical current density J{sub c} decrease for low doping (x = 0.03 wt%) then increase (x = 0.10 and 0.50 wt%) for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} doped in Y123. The transport properties of the (Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}){sub x}/YBa{sub 2}Cu{sub 3}O{sub 7}-{sub δ} composite as electrical resistance R, T{sub c}, and J{sub c} are interpreted according to Bean’s critical state model and charge-vortex interaction combined with vortex pinning in Y123 high-T{sub c} mixed-state type-II superconductor. Highlights: The critical current density J{sub c} decreased for low doping of nanosized Ni-Zn ferrite into Y123 with ratio of 0.03 wt% and increased by increasing doping ratio to 0.50 wt%. The physical properties are improved by the coexistence of the superconductor Y123 and nanosized Ni-Zn ferrites in nanocomposite material.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Magnetic Properties and Electronic Structure of Ni/C Multilayer Films

The magnetic properties of Ni/C multilayers were investigated using vibrating sample magnetometer and ferromagnetic resonance (FMR). Spin wave resonances were seen in FMR and the spin wave was found to be sustained through whole layers. The interlayer coupling constant was small pointing out a weak exchange coupling between Ni films through C spacers. The FMR linewidth, in parallel geometry, of the uniform mode decreases with the increase in Ni thickness from 30 to 300 Å which can be understood by considering interfacial effects. The magnetization decreases with decreasing Ni thickness due to the structural imperfections associated with the presence of Ni{sub 1−x}C{sub x} alloys at the interface. Density functional theory (DFT) has been performed to shed light on the decrease in magnetic moment at the interfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Origin of Interfacial Magnetic Anisotropy in Ta/CoFeB/MgO and Pt/CoFeB/MgO Multilayer Thin Film Stacks

Interfacial perpendicular magnetic anisotropy (PMA) in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO and Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO multilayer structures has been researched at various CoFeB layer thicknesses. Magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer (VSM) measurements show that while strong PMA is achieved in Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO structure for the thickness of Co{sub 40}Fe{sub 40}B{sub 20} range from 0.5 to 1.0 nm, a very weak PMA is observed in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO film stack for the same Co{sub 40}Fe{sub 40}B{sub 20} thicknesses. Based on the experimental results, the interfacial anisotropy energy in Ta/Co{sub 40}Fe{sub 40}B{sub 20}/MgO (1.17 erg/cm{sup 2}) was found to be almost 2.5× larger than that in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO (0.43 erg/cm{sup 2}). It is accepted that the PMA comes from the seed/ferromagnetic and ferromagnetic/oxide layer interfaces. Thus, the origin of interfacial magnetic anisotropy can be hybridization and/or crystallinity properties at the interfaces in Ta- and Pt-seeded stacks. While the PMA is strong in Pt/Co/MgO structure, it becomes in-plane in Fe-rich Pt/CoFeB/MgO structure. It is deduced that hybridization between 3d-5d (Co-Pt) orbitals is more dominant in Pt/CoFeB interface than 2p-3d (O-Fe) hybridization at CoFeB/MgO interface in Pt-seeded stacks. In addition, the crystallinity was studied by performing high-resolution x-ray diffraction (HR-XRD) technique. The crystal orientations of Ta and Pt are found as (002) and (111), respectively. The ferromagnetic layer might be induced out-of-plane orientation in Ta-seeded stack due to observing highly crystallized MgO (001). Thus, another reason for in-plane magnetic anisotropy in Pt/Co{sub 40}Fe{sub 40}B{sub 20}/MgO might be the absence of MgO crystallization because Pt is crystallized fcc (111) orientation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Structural and Magnetic Properties of Co{sub 100−x}Pd{sub x} Thin Films Evaporated on Si (100) Substrate

The structural and magnetic properties of Co{sub 100−x}Pd{sub x} thin films grown under vacuum by physical vapor deposition (PVD) on Si (100) are reported. The thicknesses of the samples were measured with a DEKTAK 150 profilometer; chemical composition was analyzed by energy dispersive X-ray analyses (EDX). Microscopic characterizations of the films were done with X-ray diffraction (XRD) and we conclude that all the samples were polycristalline with an hcp structure. The hysteresis loops are performed by means of vibrating sample magnetometer (VSM) and we point up that all the samples present a planar ferromagnetic anisotropy. The saturation magnetization decreases as the palladium content increases and high values of the squareness up to 0.62 were measured. All these results are analyzed and correlated.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Improvement of the Superconducting Properties of GdBa{sub 2}Cu{sub 3}O{sub 7-δ} with Nano-Sized Ferrite Addition

We have been investigating the effect of (CoFe{sub 2}O{sub 4}){sub x} and (ZnFe{sub 2}O{sub 4}){sub x} (x is the wt%) nano-sized ferrites on the superconducting (SC) properties of the high-T{sub c} SC compound GdBa{sub 2}Cu{sub 3}O{sub 7-δ} (Gd123) prepared by the conventional solid-state reaction technique. In this work, the magnetic hysteresis for pure Gd123 samples and samples added with nano-sized ferrites was measured using a superconducting quantum interference device (SQUID) magnetometer using a dc field up to 30,000 Oe. The magnetic J{sub c} was estimated using the extended Bean model. While a clear increase in J{sub c} values with the addition of (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrites is observed, a less clear positive effect on the J{sub c} values is observed with the addition of (ZnFe{sub 2}O{sub 4}){sub x} nano-sized ferrites. These results indicate an improvement of grain connectivity, decrease of voids between the grains, and decrease of porosity in Gd123 compound resulting from CoFe{sub 2}O{sub 4} addition consistent with the mechanical properties measured before. (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrite addition has thus resulted in an improvement in the SC properties of Gd123 high-T{sub c} SC compound making it more convenient for applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗