Magnetization fluctuations in nominally stable ferromagnetic materials
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High Magnetic Field Science↗
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Magnetization fluctuations in nominally stable ferromagnetic materials
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High Magnetic Field Science↗
Utilization of Ferromagnetic Material to Boost RFID Signal in Situations with Metal Interference
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Engineering - Instrumentation related to nuclear s↗
Remanent Magnetic Flux Distribution in Superconducting-Ferromagnetic Layered Heterostructures
Stacks of superconducting tape, made of second-generation coated conductors, present an interesting alternative to bulk superconductors. The layered geometry allows incorporation of other functional, namely ferromagnetic, materials. The ferromagnetic material changes the field configuration within the superconductor and can be used to shape or divert the flux density from its interior. This can be used to optimise the remanent flux density after magnetisation. FEM simulations are employed to test the performance of a variety of superconductor/ferromagnet structures and explain the role of the ferromagnetic material in the composite structure. Cases where trapped field is much higher and lower than remanent magnetisation of the ferromagnetic material are considered, showing that performance can be enhanced or maintained by using ferromagnetic material while reducing the usage of costly superconducting tape.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Gyromagnetic nonlinear transmission line for radio frequency signal generation and pulse compression
Disclosed are non-linear transmission lines using ferromagnetic materials to generate ferromagnetic resonance oscillations. In one aspect, a non-linear transmission line apparatus is disclosed. The apparatus includes an outer conductor having a first side and a second internally facing side, and an inner conductor positioned internal to the non-linear transmission line apparatus. The apparatus further includes a ferromagnetic material surrounding the inner conductor, wherein the ferromagnetic material comprises nanoparticles of an ε-polymorph of iron oxide expressed as ε-Fe2O3. The apparatus also includes a first dielectric material positioned between the outer conductor and the inner conductor, the dielectric material in contact with both the ferromagnetic material and with the second internally facing side of the outer conductor, wherein the outer conductor, the inner conductor, the dielectric material and the ferromagnetic material form the nonlinear transmission line.
Schneider, Joseph Devin↗
Nanodevice, method of making the same, and method of using the same
A nanodevice provides for electric-field control of magnon-QSD interactions. The nanodevice includes a ferroelectric substrate, a ferromagnetic material disposed over the ferroelectric substrate, and a nanodiamond including an ensemble of nitrogen-vacancy (NV) spins, each NV magnetically interfacing with the ferromagnetic material. An electric field is measured by applying a voltage across the ferroelectric substrate and the ferromagnetic material, changing a magnon excitation spectrum of the ferromagnetic material with respect to an electron spin resonance frequency of the ensemble of NV spins, and measuring a relaxation rate of the ensemble of NV spins.
Shalaev, Vladimir M.↗
Dynamics of MHD instabilities near a ferromagnetic wall
Prospective fusion component testing and DEMO power reactor concepts are expected to employ low-activation ferritic steels because of their ability to withstand the high neutron flux of the reactor environment. However, theory suggests that ferromagnetic material may amplify certain external MHD instabilities. Using its ferromagnetic-resistive wall mode (FRWM) upgrade, the High Beta Tokamak-Extended Pulse (HBT-EP) experiment has observed approximately doubled growth rates when operating with a close-fitting ferromagnetic first wall, compared to operation with a stainless steel first wall. The presence of a ferromagnetic wall correlates with earlier disruptions, and FRWM growth rates increase with decreasing mode rotation, as expected due to the increased skin depth allowing greater mode interaction with the bulk ferromagnetic material. It is also seen that introducing low-n asymmetries into the toroidal distribution of ferromagnetic material, similar to the ITER test blanket module toroidal asymmetry, changes the phase preference of rotating modes; meanwhile, a similar change in purely conducting material does not significantly change the mode's phase preference.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Effect of capping material on interfacial ferromagnetism in FeRh thin films
The role of the capping material in stabilizing a thin ferromagnetic layer at the interface between a FeRh film and cap in the nominally antiferromagnetic phase at room temperature was studied by x-ray magnetic circular dichroism in photoemission electron microscopy and polarized neutron reflectivity. These techniques were used to determine the presence or absence of interfacial ferromagnetism (FM) in films capped with different oxides and metals. Chemically stable oxide caps do not generate any interfacial FM while the effect of metallic caps depends on the element, showing that interfacial FM is due to metallic interdiffusion and the formation of a ternary alloy with a modified antiferromagnetic to ferromagnetic transition temperature.
36 MATERIALS SCIENCE↗
Characteristics of Ferromagnetic Flux Focusing Lens in the Development of Surface/Subsurface Flaw Detector
Electromagnetic NDE techniques have in the past steered away from the use of ferromagnetic materials. Although their high permeabilities lead to increased field levels, the properties of ferrous elements in the presence of alternating magnetic fields are difficult to determine. In addition, their use leads to losses which can be minimized through the use of low conductivity ferrites. In fact, the eddy current probes which do incorporate ferromagnetic materials have focused on these losses and the shielding which can be obtained by surrounding a probe with a high permeability, conducting material. Eddy current probes enclosed in conducting and magnetic shields have been used to prevent the generated fields from interacting with materials in the vicinity of the probe, such as when testing near material boundaries. A recent invention has used ferromagnetic shielding to magnetically separate individual concentric eddy current probes in order to eliminate cross-talk between the probes so that simultaneous detection of different types of flaws at different depths can be achieved. In contrast to the previous uses of ferromagnetic materials purely as magnetic shields, an electromagnetic flaw detector recently developed at NASA Langley Research Center takes advantage of the flux focusing properties of a ferromagnetic mild steel in order to produce a simple, effective device for the non-destructive evaluation of conducting materials. The Flux Focusing Eddy Current Probe has been shown to accurately measure material thickness and fatigue damage. The straight forward flaw response of the probe makes the device ideal for rapid inspection of large structures, and has lead to its incorporation in a computer controlled search routine to locate fatigue crack tips and monitor experimental fatigue crack growth experiments.
Wincheski, Buzz↗
Statistics on magnetic properties of Co compounds: A database-driven method for discovering Co-based ferromagnets
The search for new ferromagnetic compounds is often targeted at known structure families, particularly those containing iron, cobalt, and manganese. Here, we propose a method to expand this search to lesser-known structure types, using a database of experimental Curie and Néel temperatures. This study, in particular, illustrates the case of compounds containing the element cobalt, and we demonstrate how the use of such a database can lead to the discovery of ferromagnetic materials that had previously been overlooked. We report statistics from a literature survey of the magnetic properties of Co-based compounds with more than 33 at. % Co. We classify more than 13 000 compounds by structure type, cobalt content, and magnetic ground state. From these data, compounds TaCo 2 Ga, La 6 Co 13 Bi, and Nd 2 Co 3 were identified as potential ferromagnets, and we confirm their ferromagnetic ordering theoretically via first-principles calculations and experimentally via synthesis and characterization measurements. In addition, the analysis is focused on the collection of data trends and discovery of ferromagnetic materials with easy-axis magnetic anisotropy. Both known ferromagnetic materials with unknown magnetic anisotropy, and unstudied compounds were considered. From the subset of known ferromagnets with unknown anisotropy, the compound Co 2 Mg was synthesized, characterized, and determined to have easy-axis magnetic anisotropy at room temperature.
36 MATERIALS SCIENCE↗
Topological insulator-based high efficiency switching of magnetic unit, method and applications
A magneto-electronic device may include: a spin-orbit torque (SOT) generator layer; a magnetic memory layer; and/or sensing electrodes configured to measure a Hall effect of the magnetic memory layer. The SOT generator layer may include topological insulator material, and the magnetic memory layer may include ferromagnetic material with perpendicular magnetic anisotropy. A magneto-electronic device may include: a spin-orbit torque (SOT) generator layer; a first magnetic memory layer on the SOT generator layer; an insulating layer on the first magnetic memory layer; and/or a second magnetic memory layer on the insulating layer. The SOT generator layer may include topological insulator material. The first magnetic memory layer and the second magnetic memory layer may include ferromagnetic material with either perpendicular magnetic anisotropy or in-plane magnetic anisotropy.
36 MATERIALS SCIENCE↗
Ultrahigh-spatial-resolution chemical and magnetic imaging by laser-based photoemission electron microscopy
We report the first experiments carried out on a new chemical and magnetic imaging system, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with a continuous-wave deep-ultraviolet laser. Threshold photoemission is sensitive to the chemical and magnetic structures of the surface of materials. The spatial resolution of PEEM is limited by space charging when using pulsed photon sources as well as aberrations in the electron optics. We show that the use of a continuous-wave laser enabled us to overcome such a limit by suppressing the space-charge effect, allowing us to obtain a resolution of approximately 2.6 nm. With this system, we demonstrated the imaging of surface reconstruction domains on Si(001) by linear dichroism with normal incidence of the laser beam. We also succeeded in magnetic imaging of thin films with the use of magnetic circular dichroism near the Fermi level. The unique features of the ultraviolet laser will give us fast switching of the incident angles and polarizations of the photon source, which will be useful for the characterization of antiferromagnetic materials as well as ferromagnetic materials.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Development of electroplated magnetic materials for MEMS
Soft ferromagnetic materials have thus far found the most utility in magnetic-MEMS, because the technologies necessary for depositing and micromachining them have been well developed previously by the data storage industry.
MEMS magnetic materials↗
Superconductive magnetic-field-trapping device
An apparatus which enables the establishment of a magnetic field in air that has the same intensity as the ones in ferromagnetic materials is described. The apparatus is comprised of a core of ferromagnetic material and is surrounded by a cylinder made of a material that has superconducting properties when cooled below a critical temperature. A method is provided for producing a magnetic field through the ferromagnetic core. The core can also be split and pulled apart when it is required that the center of the cavity be left empty.
Hildebrandt, A. F.↗
Iron abundance in the moon from magnetometer measurements
Apollo 12 and 15 lunar surface magnetometer data with simultaneous lunar orbiting Explorer 35 data are used to plot hysteresis curves for the whole moon. From these curves a whole-moon permeability mu = 1.029 + 0.024 or - 0.019 is calculated. This result implies that the moon is not composed entirely of paramagnetic material, but that ferromagnetic material such as free iron exists in sufficient amounts to dominate the bulk lunar susceptibility. From the magnetic data the ferromagnetic free iron abundance is calculated. Then for assumed compositional models of the moon the additional paramagnetic iron is determined, yielding total lunar iron content. The calculated abundances are as follows: ferromagnetic free iron = 5 + or - 4 wt. percent, and total iron in the moon = 9 + or - 4 wt. percent.
Parkin, C. W.↗
Iron abundance in the moon from magnetometer measurements
Apollo 12 and 15 lunar surface magnetometer data with simultaneous lunar orbiting Explorer 35 data are used to plot hysteresis curves for the whole moon. From these curves a whole-moon permeability of 1.029 (+0.024 or -0.019) is calculated. This result implies that the moon is not composed entirely of paramagnetic material, but that ferromagnetic material such as free iron exists in sufficient amounts to dominate the bulk lunar susceptibility. From the magnetic data the ferromagnetic free iron abundance is calculated. Then for assumed compositional models of the moon the additional paramagnetic iron is determined, yielding total lunar iron content. The calculated abundances are as follows: ferromagnetic free iron, 5 plus or minus 4 wt %; total iron in the moon, 9 plus or minus 4 wt %.
Parkin, C. W.↗
Gas sensor
A gas sensor is described which incorporates a sensor stack comprising a first film layer of a ferromagnetic material, a spacer layer, and a second film layer of the ferromagnetic material. The first film layer is fabricated so that it exhibits a dependence of its magnetic anisotropy direction on the presence of a gas, That is, the orientation of the easy axis of magnetization will flip from out-of-plane to in-plane when the gas to be detected is present in sufficient concentration. By monitoring the change in resistance of the sensor stack when the orientation of the first layer's magnetization changes, and correlating that change with temperature one can determine both the identity and relative concentration of the detected gas. In one embodiment the stack sensor comprises a top ferromagnetic layer two mono layers thick of cobalt deposited upon a spacer layer of ruthenium, which in turn has a second layer of cobalt disposed on its other side, this second cobalt layer in contact with a programmable heater chip.
47 OTHER INSTRUMENTATION↗
Validation of plasma shape reconstruction by Cauchy condition surface method in KSTAR
Cauchy Condition Surface (CCS) method is a numerical approach to reconstruct the plasma boundary and calculate the quantities related to plasma shape using the magnetic diagnostics in real time. It has been applied to the KSTAR plasma in order to establish the plasma shape reconstruction with the high elongation of plasma shape and the large effect of eddy currents flowing in the tokamak structures for the first time. For applying the CCS calculation to the KSTAR plasma, the effects by the eddy currents and the ferromagnetic materials on the plasma shape reconstruction are studied. The CCS calculation includes the effect of eddy currents and excludes the magnetic diagnostics, which is expected to be influenced largely by ferromagnetic materials. Calculations have been performed to validate the plasma shape reconstruction in 2012 KSTAR experimental campaign. Comparison between the CCS calculation and non-magnetic measurements revealed that the CCS calculation can reconstruct the accurate plasma shape even with a small I{sub P}.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗