Search NASA⌕ Search

SEARCH · Search NASA

Results for “MAGNETIC PROPERTIES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Low-Temperature Magnetic Properties of Superconducting Indium Nanocomposites in Opal Matrix

We studied magnetic properties of the In–opal nanocomposite, which is a close-packed system of SiO{sub 2} spheres of the same diameter D with metal-filled cavities (series of opal structures with D = 190, 230, and 290 nm were studied). The dependencies of the samples’ magnetization m on temperature T, as well as on external magnetic field H, were measured at various temperatures below the critical temperature T{sub c} of the superconducting (SC) transition. The critical temperature T{sub c} and the critical magnetic field H{sub c} were measured. Magnetization jumps were observed in m(H) dependences at temperatures below 2.6 K. It was found that the jumps are quasiperiodic as functions of H, and the number of jumps increases both with increase in the sweeping rate dH/dt, as well as with decrease in the characteristic size of the In inclusions in the nanocomposite. A model describing the breakup of the SC state with an increase in the external magnetic field is proposed. According to this model, when the screening current reaches a critical value in the near-surface layer of the nanocomposite, an avalanche-like penetration of the field into the volume of the nanocomposite occurs. After this, the SC state is restored, and the magnetic field “freezes” in the structure of the nanocomposite.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Switchable electronic and enhanced magnetic properties of CrI 3 edges

Owing to its novel electronic and magnetic properties, two-dimensional CrI 3 has great potential in the application of spintronic devices. However, as an inevitable line defect, the properties of the edges of CrI 3 remain elusive. Here, via first-principles calculations with spin–orbit coupling, we investigated the thermodynamic stabilities, electronic and magnetic properties of thirteen CrI 3 edges with different structures. We showed that zigzag edges are more stable than armchair edges, and a CrI 3 nanoribbon can be either metallic or insulating depending on its chemical growth conditions. Here, the edge stability and associated electronic properties can be understood in terms of the octahedron ligand field and electron counting model. In most cases, both the magnetic moment and Curie temperature can be enhanced by edges, which are in startle contrast to the surfaces of three-dimensional ferromagnetic materials, where a magnetic dead layer is often observed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Unraveling Site Selective Magnetic Properties of Cobalt Sites in Critical Elements Lean RE(TM)5 Magnet Materials

We report here our discovery of crystallographic and interstitial sites and onsite electron correlation propelled intrinsic and derived permanent magnetic properties of critical elements lean RE(TM) 5 (RE = La, Ce and TM = Fe, Co) magnet materials. A full potential linearized augmented plane wave (FP-LAPW) method within the local density approximation (LDA) is used to investigate and analyze the electronic structure and magnetism of these RE(TM) 5 type structures. To better correlate the experimental results, the effective Coulomb (U) and exchange (J) interactions (Hubbard parameters) are crucial at the transition metal sites. Results show that the main propeller of magnetic anisotropy in these compounds is the cobalt atoms at the 2c sites not the 3g sites. This site-specific property and site preference energetics are used to replace 3g sites with non-critical elements such as iron that exhibits a larger magnetic moment. Based on this strategic replacement, we predict two new compounds that have a larger hardness parameter with a relatively large energy product due to the atomic dilution caused by interstitial addition of nitrogen in the compounds: CeCo 2 Fe 3 N 2 and LaCo 2 Fe 3 N 2 .

Rare-earths↗
DOE OSTI2021

Temperature-Dependent Magnetic Properties of Magnetorheological Elastomers

We report on an investigation of the temperature-dependent magnetic properties of magnetorheological elastomers (MREs). These are a class of composites that consist of magnetically permeable particles dispersed in a nonmagnetic polymeric matrix. Under the application of an external magnetic field, a large deformation occurs altering the mechanical properties of these materials. Due to their magnetoelastic coupling response, these materials are finding an increasing interest among the scientific community. These polymer-based composites’ performance depends on many factors, which temperature is one of the biggest influencing factors requiring further investigation. In this work, the magnetic properties of isotropic and anisotropic polyurethane-based MRE with different iron (Fe) particle loading fractions (50, 60, 70, and 80% by weight) were investigated under different temperatures. From the analysis, the magnetization curves of these materials are observed to overlap for the different measured temperature values. The variation of various magnetic properties including saturation magnetization and differential susceptibility with temperature was also determined. Furthermore, the results show ~ 2.5% decrement in the saturation magnetization for each of the loading fractions, between the lowest (300K) and the highest (400K) measured temperature. On the other hand, the initial differential susceptibility exhibits different trends with increasing temperature. Generally, the magnetization response of these materials is seen to be only slightly sensitive to temperature changes. Additionally, the magnetization response is observed to be highly dependent on particle loading fractions and particle orientation within the elastomer.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis, crystal structure and magnetic properties of K Ln Se 2 ( Ln = La, Ce, Pr, Nd) structures: A family of 2D triangular lattice frustrated magnets

Here, we report the detail synthesis, single crystal structure characterization and magnetic properties of KLnSe 2 series obtained via solid state molten flux growth method. The crystal structures were characterized using single crystal x-ray diffraction. The KLnSe 2 (Ln = La, Ce, Pr and Nd) series crystallizes in the trigonal crystal system with the space group of R-3m (No. 166). The overall structure contains two-dimensional (2D) layers made from edged shared LnSe 6 -octahedra. Ln 3+ ions form a perfect triangular magnetic lattice which propagates along ab-plane. These triangular lattices are separated by the K + ions. The magnetic properties confirm that, Ce, Pr and Nd do not show any long-range ordering down to 0.4 K indicating frustrated magnetism in the KLnSe 2 series.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of Ge substitution on magnetic properties in the itinerant chiral magnet MnSi

We have investigated the effect of Ge substitution on the magnetic ordering in the B20 itinerant chiral magnet MnSi prepared by melting and annealing under ambient pressure. From a metallurgical survey, the solubility limit of Ge was found to be x = 0.144(5) with annealing temperature T an = 1073 K. Magnetization measurements on MnSi 1–x Ge x samples show that the helical ordering temperature T c increases rapidly in the low-x range, whereas it becomes saturated at higher concentration x > 0.1. Here, the Ge substitution also increases both the saturation magnetization M s and the critical field to the fully polarized state H c2 . In contrast to the saturation behavior of T c , those parameters increase linearly up to the highest Ge concentration investigated. In the temperature-magnetic field phase diagram, we found enlargement of the skyrmion phase region for large x samples. We, furthermore, observed the nonlinear behavior of helical modulation vector k as a function of Ge concentration, which can be described qualitatively using the mean field approximation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Theoretical Correlation of Elemental Distribution of Nd and Pr in Ce-Fe-B Microstructure With Hard Magnetic Properties

Relatively resource-rich but property inferior-Ce-Fe-B magnet can be improved by partial replacement of Ce by Nd and/or Pr. In addition to the amount of Nd/Pr, their distribution profile in microstructure plays an important role. From our first principles density functional theory (DFT) calculation, the substitution energy of Ce by Pr/Nd is negative in Ce 2 Fe 14 B (2:14:1) while that for laves phase, CeFe 2 is positive, implying that Nd/Pr stabilize 2:14:1 and suppress the formation of the CeFe 2 phase. Further, micromagnetic simulation indicates that homogenized distribution of Nd/Pr improves squareness of demagnetization curve, while core (Ce-rich)-shell (Nd/Pr-rich) 2:14:1 grain structure enhances coercivity. Magnetic properties of Ce-Fe-B can be optimized by manipulating distribution profile of chemical element in microstructure based on their subtle difference in thermodynamic property, which is an effective pathway to design optimized chemical composition and processing route for high-performance magnet.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Magnetic Properties of Simplest Pure Husimi Lattice: a Monte Carlo Study

The magnetic properties of a Husimi lattice with antiferromagnetic spins-|S| = 1/2, 1, 3/2, and 2 Ising model with three sites in the elementary polygon (p = 3) and the coordination number z = 4 have been investigated using a Monte Carlo study. The reduced critical temperature is deduced for different values of magnetic external field, for a fixed value of crystal field and spin moments. The magnetization versus the crystal field is determined for different values of temperatures and for different values of external magnetic field and spin moments. The hysteresis curves of magnetization with the magnetic field have been established for different values of reduced temperatures, reduced crystal field, and spin moments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Electronic, structural and magnetic properties of Mn (1+x) Pt (1-x) Sb

Electronic and magnetic properties of half-metallic Heusler alloys can be modified by tuning their chemical compositions. We have carried out a combined theoretical and experimental investigation of Mn (1+x) Pt (1-x) Sb (0 ≤ x ≤ 0.5) alloys. Our first-principles calculations indicate that the stoichiometric MnPtSb exhibits nearly half-metallic band structure, but a robust half-metallicity can be achieved in Mn-rich compositions Mn (1+x) Pt (1-x) Sb (0 ≤ x ≤ 0.5) with x = 0.25 and higher in their cubic structures. In addition, while MnPtSb exhibits ferromagnetic alignment, Mn (1+x) Pt (1-x) Sb are ferrimagnetic for all non-zero values of x. We have also synthesized cubic MnPtSb and Mn 1.25 Pt 0.75 Sb alloys using arc melting and annealing. The magnetic properties of these alloys are consistent with our theoretical predictions. Furthermore, these results indicate that the Mn-rich Mn (1+x) Pt (1-x) Sb alloys have potential for spin-transport-based devices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure and magnetic properties of ultrathin FePt granular films

FePt granular films with grain size smaller than 10 nm are promising candidates for storage media used in the next generation heat-assisted magnetic recording technology. However, FePt films show degraded magnetic properties when the grain size is reduced to this scale, which cannot be explained solely by the finite size theory. In this study, we explored the structural cause of property degradation by employing advanced electron microscopy and atomistic modeling. Structural features unique to the nanostructured FePt granular films at significantly reduced grain sizes of 2~8 nm were studied by high-resolution scanning transmission electron microscopy with geometric aberrations corrected up to the third order. Two critical structural parameters, the threshold grain size corresponding to the upper size limit of the FePt grains with zero chemical ordering and the sub-nanometer thin interfacial impurity at grain boundaries, were identified. A new atomistic model was developed to correlate these structural characteristics with key magnetic properties such as Curie temperature, saturation magnetization, magnetocrystalline anisotropy, and their grain-to-grain variation. The model shows good agreement with the experimental magnetic data and explains the gap in magnetic properties between the bulk and nanostructured FePt.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tuning the Magnetic Properties of ZnFe{sub 2}O{sub 4} Nanoparticles Through Partial Doping and Annealing

The aim of this study was to investigate the effect of annealing temperature and cobalt cation (Co{sup 2+}) doping on the magnetic properties of zinc ferrite (ZFO) nanoparticles. The nanoparticles were prepared through sol-gel combustion process with citric acid as the fuel. The obtained nanoparticles were annealed at several temperatures from 300 to 1000 °C for 2 h. Spinel formation was proved by X-ray diffraction (XRD) patterns, and the average crystallite size in all samples was estimated between 22 and 32 nm. It is worthwhile to mention that Fe{sub 2}O{sub 3} and ZnO are detected as the medium phases. Meanwhile, Fe{sub 2}O{sub 3} phase transformation to the other allotropes has happened around 400 °C and was characterized via the simultaneous thermal analysis (STA) and XRD. For higher annealing temperatures, diffusion has gradually been completed and, finally, the single phase of spinel structure was prepared at 1000 °C. In addition, field-emission scanning electron microscopy (FESEM) images revealed that the nanoparticle size after annealing was between 30 and 200 nm for the whole samples. The formation of the spinel phase was considered the most important factor on the magnetic properties of ZFO. Cobalt doping, annealing temperature, and also Fe{sub 2}O{sub 3} phase were the main factors on changing magnetic properties. Paramagnetic nanoparticles with higher coercivity for doped samples rather than un-doped samples have been obtained.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Tunable structural and magnetic properties of NiAs-type Mn x Sb (1.00≤x≤1.30) compounds

Mn-based alloys can exhibit a variety of magnetic properties related to their tunable exchange interactions. Here, structural and magnetic properties of hexagonal NiAs-type Mn x Sb (1.00≤x≤1.30) compounds are studied with a combination of X-ray diffraction, neutron diffraction, and magnetic measurements. It is found that the magnetization, Curie temperature, and magnetocrystalline anisotropy of Mn x Sb compounds can be tuned by controlling Mn concentration and doping at interstitial (2d) sites. With increasing Mn concentration, magnetic moments of Mn atoms decrease and deviate gradually from the ab-plane to the c-axis for 1.20≤x≤1.22 at room temperature, which leads to a decrease of the Curie temperature T c and the spin reorientation temperature T SR . By doping with nonmagnetic elements, a substantial room-temperature magnetocaloric effect without magnetic hysteresis was achieved for Mn 1.12 Zr 0.1 Sb compound, which is highly beneficial to the practical magnetic refrigeration application.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of magnetic field annealing on the hard magnetic properties of milled Nd-Fe-B powders

In this study, we report the effect of magnetic field annealing (MA) in relieving the stress induced during the milling of Nd-Fe-B sintered magnets. The effect of MA processing parameters and particle size on the magnetic properties were investigated. Based on the results, magnetic field annealing is more effective in improving the magnetic properties of larger size particles, compared to finer particles. Our computational study on the role of particle surface defects in bi-modal particle distribution agrees with results obtained experimentally. In conclusion, magnetic field annealed powder has been successfully used to develop 4.6 g.cm -3 density bonded magnets with 75 vol% of magnetic powder and polyamide 12 (nylon 12) polymer binder resulting in 11.3 MGOe energy product.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnetic Properties of Eu{sub 0.9}Yb{sub 0.1}B{sub 6}

The magnetic properties of substitutional solid solutions Eu{sub 0.9}Yb{sub 0.1}B{sub 6} have been investigated in the temperature range of 2–300 K in fields up to 5 T. The data obtained confirm that the state with the electronic and magnetic phase separation (typical of europium hexaboride) is implemented in Eu{sub 0.9}Yb{sub 0.1}B{sub 6} when the system metallization (T{sub M} ≈ 15 K) precedes the ferromagnetic ordering (T{sub C} ≈ 11.4 K). An analysis of the curves M(H) in the Belov–Arrott coordinates makes it possible to evaluate spontaneous magnetization M{sub sp} and zero field susceptibility χ{sub 0} and determine the character of their critical behavior near the Curie point. The calculated critical indices (γ ≈ 1.28 and β ≈ 0.34) are in agreement with the predictions of the three-dimensional Heisenberg model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effects of Interface Induced Natural Strains on Magnetic Properties of FeRh

FeRh is a unique alloy which shows temperature dependent phase transition magnetic properties. The lattice parameter (a) of this CsCl-type (B2) structure is 4.1712 Å. It undergoes a first order transition from antiferromagnetic (AFM) to ferromagnetic (FM) order at around 370K and hysteretic behavior while cooling and heating. This meta-magnetic transition of FeRh is accompanied by an isotropic expansion in the unit cell volume, which indicates strong coupling between magnetic and structural properties of FeRh. Consequently, the magnetic and transport properties, such as magnetoresistance (MR), are changed during the transition. Due to its unique thermo-magnetic behaviors, FeRh is very important for future spintronic devices. The structure could be applicable for MR devices such as memory, sensors, and many other applications. It is critical to understand how to systematically influence phase transition of FeRh from naturally applied strains. Here, we investigate magnetic properties of FeRh in different strain environments induced by the substrates with different lattice parameters. The study was performed using synchrotron radiation, temperature dependent magnetometry, and magnetic scanning probe microscopy in addition to Landau theory calculations. We found that the naturally induced strains could modulate the magnetic phase locally and globally. The presence of the segments from the nucleation of the ferromagnetic domains, with a very thin layer in the antiferromagnetic matrix and the domain growth, were observed gradually. Using the systematic phenomena, it could be used for immediate applications in the future generation of phase change random access memory (PC-RAM) devices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Ti on structure and soft magnetic properties of Si-rich Finemet-type nanocrystalline Fe73.5Cu1Nb3-xSi17.5B5Tix alloys

Highlights: • Substitution of Nb by Ti can reduce the T{sub x1} and enlarge the ΔT{sub x}. • Fe{sub 73.5}Cu{sub 1}Nb{sub 2}Si{sub 17.5}B{sub 5}Ti{sub 1} alloy exhibits high μ{sub i} of 18,000 and low H{sub c} of 0.54 Oe. • Magnetic properties were analysed in terms of the relationship between H{sub c} and μ{sub i}. • Soft magnetic properties will deteriorate when Nb is completely replaced by Ti. • The reasons of variation of permeability at high temperature were analyzed. - Abstract: Fe{sub 73.5}Cu{sub 1}Nb{sub 3-x}Si{sub 17.5}B{sub 5}Ti{sub x} (x = 0, 1, 2, 3) amorphous alloys were prepared by the single roller melt spinning method. The effects of Ti substitution for Nb on the crystallization behavior, microstructure and soft magnetic properties were investigated. Compared to the previously reported Finemet alloy, the onset primary crystallization temperature T{sub x1} becomes lower which has dropped from 803K to 758K. The crystallization temperature interval ΔT{sub x} increases from 468K to 488K as the x increases from 0 to 3. However, the Curie temperature of amorphous phase shows a downward tendency with the increase of Ti content. Compared to the previously reported Finemet alloy, the μ{sub i} increases obviously to more than 18,000 at x = 1, the H{sub c} decreases from 0.59 Oe to 0.54 Oe. When Ti replaces Nb completely, the optimum annealing temperature range for precipitating single soft magnetic phase is enlarged, but the permeability at room- and high-temperature is deteriorated, the reason of which was also analysed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Investigation of Microstructural and Magnetic Properties of BaV{sub x}Fe{sub 12−x}O{sub 19} Nanohexaferrites

Nanohexaferrites of BaV{sub x}Fe{sub 12−x}O{sub 19} (0.0 ≤ x ≤ 0.1) were prepared using sol–gel auto-combustion. The structure and morphology of BaV{sub x}Fe{sub 12−x}O{sub 19} (0.0 ≤ x ≤ 0.1) nano-sized hexaferrites were explored by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDXS. XRD analysis indicated particle size in the 55–60-nm interval. SEM and EDXS investigations confirmed the formation of the desired composition of V-substituted Ba-hexaferrites. The magnetic properties of products were studied. The magnetic M(H) hysteresis loops revealed that all produced nanohexaferrites display ferromagnetic-like comportment. The deduced saturation magnetization (M{sub s}), retentivity (M{sub r}), magneto-crystalline anisotropy fields (H{sub a}), and coercive field (H{sub c}) were enhanced for low V{sup 3+} contents and were maximum for BaV{sub 0.04}Fe{sub 11.96}O{sub 19} (x = 0.04) nanohexaferrites, showing the strengthening of magnetic properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗