Magnetic properties of selected spacecraft materials
Summary data on investigation of magnetic properties of selected spacecraft materials
Droll, P. W.↗
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Magnetic properties of Apollo samples and implications for regolith formation
The magnetic properties of a number of Apollo 17 samples have been measured and confirm that regoliths of mare sites (Apollo 11, 12, 15 valley, and 17 valley) differ markedly from those of highland sites (Apollo 14, 16, and 17 massif) in the ratio of content of metallic to ferrous iron and in the grain size of metallic iron. The ratio of metallic to ferrous iron is correlated with mean particle size, a parameter representing maturity, for soils of Apollo 16 and roughly correlated with the age of the sites for soils of different sites. It is suggested that the ratio of metallic to ferrous iron may be an effective indicator of relative soil maturity for any one site and of the age of the soil material for any sites.
Pearce, G. W.↗
Structural, Vibrational, and Magnetic Properties of MoS{sub 2}/Cr{sub 2}O{sub 3} Composites Synthesized by the Solid-State Technique
(1− x) Cr{sub 2}O{sub 3}/x MoS{sub 2} (x = 0.25, 0.5, 0.75) were synthesized using the powder solid-state route. The structural, morphological, vibrational, and magnetic properties of the as-prepared MoS{sub 2}/Cr{sub 2}O{sub 3} samples with different Cr{sub 2}O{sub 3} contents have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy, Raman spectroscopy, and vibrating sample magnetometry (VSM), respectively. The X-ray diffraction results show the presence of the parent compounds (molybdenum disulfide (MoS{sub 2}) and chromium oxide (Cr{sub 2}O{sub 3})) in addition to a secondary phase corresponding to chromium molybdenite Cr{sub 2}Mo{sub 3}O{sub 12}. Raman and IR spectra were recorded, and the observed modes were analyzed and assigned to different normal modes of vibration. Magnetic characterizations revealed that all the series MoS{sub 2}/Cr{sub 2}O{sub 3} composites possess paramagnetic characteristics both at room temperature and at 30 K. Further, the maximum of magnetization increased with the increase of Cr{sub 2}O{sub 3} content.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Magnetic Properties of Lunar Geologic Terranes: New Statistical Results
We use global magnetic field data and digitized geologic maps to determine the magnetic properties of lunar terranes. Average fields vary by a factor of 100 from demagnetized impact basins and craters to strongly magnetized antipodal regions. Additional information is contained in the original extended abstract.
Halekas, J. S.↗
Magnetic properties of the itinerant A- type antiferromagnet CaCo 2 P 2 studied by Co 59 and P 31 nuclear magnetic resonance
59 Co and 31 P nuclear magnetic resonance (NMR) measurements in external magnetic and zero magnetic fields have been performed to investigate the magnetic properties of the A-type antiferromagnetic (AFM) CaCo 2 P 2 . NMR data, especially the nuclear spin lattice relaxation rates 1/T 1 exhibiting a clear peak, provide clear evidence for the AFM transition at a Néel temperature of T N ~ 110 K. The magnetic fluctuations in the paramagnetic state were found to be three-dimensional ferromagnetic, suggesting ferromagnetic interaction between Co spins in the ab plane characterizes the spin correlations in the paramagnetic state. In the AFM state below TN, we have observed 59 Co and 31 P NMR signals under zero magnetic field. From 59 Co NMR data, the ordered magnetic moments of Co are found to be in ab plane and are estimated to be 0.35 μ B at 4.2 K. Furthermore, the external field dependence of 59 Co NMR spectrum in the AFM state suggests a very weak magnetic anisotropy of the Co ions and also provides microscopic evidence of canting the Co-ordered moments along the external magnetic field directions. The magnetic state of the Co ions in CaCo 2 P 2 is well explained by the local-moment picture in the AFM state, although the system is metallic, as seen by 1/T 1 T = constant behavior.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Structural and Magnetic Properties of La-Substituted M-Type Hexagonal Sr–Ni Ferrites Synthesized by Ball-Milling-Assisted Ceramic Process
Sr{sub 0.5}Ni{sub 0.5}La{sub x}Fe{sub 12 − x}O{sub 19} (x = 0, 0.08, 0.16, and 0.24) hexaferrites have been synthesized by ball-milling-assisted ceramic process. The calcined samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and vibrating sample magnetometry (VSM). XRD reveals that all samples consist of the main M-type hexagonal Sr ferrite phase and a low amount of rhombohedral Fe{sub 2}O{sub 3} as secondary phase, and a continuous increase of the hexagonal lattice parameters with substitution content (x). Magnetic characterization indicates that all Sr{sub 0.5}Ni{sub 0.5}La{sub x}Fe{sub 12 − x}O{sub 19} samples have a hard magnetic property. Substitution of Fe{sup 3+} ions by La{sup 3+} ions can obviously improve the specific saturation magnetization, remanence, magnetic moment, and effective anisotropy constant. Specific saturation magnetization, remanence, and the magnetic moment reach a maximum at x= 0.24 and calcination temperature of 1050 {sup ∘}C.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Impact of Erbium Doping in the Structural and Magnetic Properties of the Anisotropic and Frustrated SrYb 2 O 4 Antiferromagnet
We present a systematic study of the structural and magnetic properties of a series of powder samples of SrYb 2-x Er x O 4 with different Yb/Er concentrations. Magnetometry and neutron diffraction have been used to study the magnetic ground states of the compound series, while inelastic neutron scattering was used to investigate the crystal field excitations for a chosen concentration. These results show that the crystal structure remains the same for all compositions, while the lattice parameters increase linearly with the Er content. All compounds showed some type of magnetic transition below 1 K, however, both the magnetic structure and nature of the phase transition vary throughout the series. The samples present a non-collinear magnetic structure with the moments lying on the ab plane for low Er content. For high Er content, the magnetic structure is collinear with the moments aligned along the c-axis. A critical concentration is found where there is a bifurcation between zero-field and field-cooled magnetic susceptibility. This irreversible process could be due to the random mixture of single-ion magnetic anisotropies.
36 MATERIALS SCIENCE↗
The Magnetic Properties Of Aggregate Polycrystalline Diamond: Implications For Carbonado Petrogenesis
Carbonados are a type of diamond, which are made up of many aggregrates of small crystalline diamonds or microdiamonds. The term "carbonado" comes from the Portuguese word carbonated. They are only found in sedimentary deposits in the Central African Republic (CAR) and the Bahia Province of Brazil. They were once the source of the world's supply of industrial diamonds. Their origin is uncertain but several mutually exclusive hypotheses have been proposed. This theories are: (1) extraterrestrial, that is they formed from the dust cloud of original solar nebulae; (2) produced by the high temperatures and pressures of the Earth's mantle; (3) or as the result of an extra-terrestrial impact into a carbon rich layer of sediment. Our study was done to further the understanding of their origin. We measured the magnetic properties on some twenty samples from the CAR. An earlier study was done on whole samples of carbonados and the "common" or kimberlitic diamond. Our work differed in that we started at the surface and subsequently removed the surface layers (by days of acid immersion) into the interior; measuring the magnetic properties at each interval. This procedure permits us to monitor the distribution of magnetic substances within the samples. Our results showed that the magnetic carriers are distributed on the surface including the open pores and that the carbonado interior is essentially non-magnetic. This result suggests that the initial formation environment was deficient in magnetic particles. Such a situation could indicate that their formation was the result of an extra-terrestrial body impacting carbon-rich sediment. Obviously, more work will be required on isotopic and chemical analyses before a more detailed ori-in can be determined.
Kleteschka, Gunther↗
Microscopic characterization of the magnetic properties of the itinerant antiferromagnet La 2 Ni 7 by La 139 NMR/NQR measurements
In this study, 139 La nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements have been performed to investigate the magnetic properties of the itinerant magnet La 2 Ni 7 , which shows a series of antiferromagnetic (AFM) phase transitions at T N1 = 61 K, T N2 = 56 K, and T N3 = 42 K under zero magnetic field. Two distinct La NMR signals were observed due to the two crystallographically inequivalent La sites in La 2 Ni 7 (La1 and La2 in the La 2 Ni 4 and the LaNi 5 subunits of the La 2 Ni 7 unit cell, respectively). From the 139 La NQR spectrum in the AFM state below T N3 , the AFM state was revealed to be a commensurate state where Ni-ordered moments align along the crystalline c axis. Owing to the two different La sites, we were able to estimate the average values of the Ni-ordered moments (0.09 – 0.10 μB / Ni and 0.17 μB / Ni around La1 and La2, respectively) from 139 La NMR spectrum measurements in the AFM state below T N3 , suggesting a nonuniform distribution of the Ni-ordered moments in the AFM state. In contrast, a more uniform distribution of the Ni-ordered moments in the saturated paramagnetic state induced by the application of high magnetic fields is observed. The temperature dependence of the sublattice magnetization measured by the internal magnetic induction at the La2 site in the AFM state was reproduced by a local-moment model better than the self-consistent renormalization (SCR) theory for weak itinerant antiferromagnets. Given the small Ni-ordered moments in the magnetically ordered state, our results suggest that La 2 Ni 7 has characteristics of both itinerant nature and localized nature in its magnetism. With this in mind, it is noteworthy that the temperature dependence of nuclear spin-relaxation rates (1/T 1 ) in the paramagnetic state above T N1 measured at zero magnetic field can be explained qualitatively by both the SCR theory and the local-moment model.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of Cysteine Substitutions on the Structural and Magnetic Properties of Fe{sub 3}O{sub 4}–Cysteine/RGO and Fe{sub 3}O{sub 4}/RGO–Cysteine Nanocomposites
We synthesized by electrostatic self-assembly route in basic solution Fe{sub 3}O{sub 4}–cysteine/RGO and Fe{sub 3}O{sub 4}/RGO–cysteine nanocomposites. In this method, electrostatic interaction was created via negatively charged surface of the reduced graphene oxide and reduced graphene oxide–cysteine sheets and positively charged surface of the Fe{sub 3}O{sub 4} and Fe{sub 3}O{sub 4}–Cys nanoparticles in aqueous solution. The structural and magnetic properties of the prepared samples were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The dependences of magnetization as a function of applied field using a vibrating sample magnetometer exhibit S-like curves, indicating a magnetic hysteresis behavior for all samples. It clearly showed that, the nanocomposites showed a reduction of saturation magnetization to the Fe{sub 3}O{sub 4} nanoparticles.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Electrical, optical, and magnetic properties of amorphous yttrium iron oxide thin films and consequences for non-local resistance measurements
We present magnetic characterization, charge resistivity, and optical photoluminescence measurements on amorphous yttrium iron oxide thin films ( a-Y–Fe–O), with supporting comparisons to amorphous germanium ( a-Ge) films. We measured magnetic properties with both SQUID magnetometry and polarized neutron reflectometry. These results not only confirm that a-Y–Fe–O is a disordered magnetic material with strong predominantly antiferromagnetic exchange interactions and a high degree of frustration, but also that it is best understood electrically as a disordered semiconductor. As with amorphous germanium, a-Y–Fe–O obeys expectations for variable-range hopping through localized electron states over a wide range of temperature. We also clarify the consequences of charge transport through such a semiconducting medium for non-local voltage measurements intended to probe spin transport in nominally insulating magnetic materials. We further compare non-local resistance measurements made with “quasi-dc” automated current reversal to ac measurements made with a lock-in amplifier. These show that the “quasi-dc” measurement has an effective ac current excitation with frequency up to approximately 22 Hz, and that this effective ac excitation can cause artifacts in these measurements including incorrect sign of the non-local resistance. Here, this comprehensive investigation of non-local resistance measurements in a-Y–Fe–O shows no evidence of spin transport on micrometer length scales, which is contrary to our original work, and in line with more recent investigations by other groups.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Martensitic Transformation and Magnetic Properties of the CuAl, CuAlMn, and CuAlMnZn Alloys
In the present work, the effect of alloying elements on the phase transformation which are formed by cooling effect in CuAl, CuAlMn, and CuAlMnZn (wt%) alloys are investigated using scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) characterization techniques. From SEM observations, the martensite formation with different morphologies is observed in these alloys. But the results of the scanning electron microscope investigations presented in this work have not formed the precipitates in the CuAl alloy with Mn or Zn additions. We found that magnetic saturation and coercivity values decreased with the addition of Mn and Zn elements to the CuAl alloy. The findings confirmed the variation in magnetic properties, which occurred in the result of adding different alloying elements.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effects of Mg Substitution on the Structural and Magnetic Properties of Ni{sub 0.2}Mg{sub x}Co{sub 0.8−x}Fe{sub 2}O{sub 4} Nanoparticle Ferrites
Sol-gel auto-combustion is a method of preparing ferrite by combining combustion with chemical gel. In this study, Ni-Mg-Co ferrite powders are prepared by coprecipitation method, and the nanocrystals of Ni{sub 0.2}Mg{sub x}Co{sub 0.8−x}Fe{sub 2}O{sub 4} are successfully synthesized. The structure and magnetic properties of undoped and Mg-substituted Ni-Co ferrite nanoparticles are systematically investigated. The methods used to characterize the prepared samples are X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and Vibrating sample magnetometry (VSM). The synthesized samples are confirmed by XRD analysis to form a single-phase cubic spinel structure with crystals between 48 and 50 nm. With the increase of Mg ion concentration, the lattice constant decreases. The results of FTIR spectroscopy indicated that a spinel structure was formed. Transmission electron microscopy (TEM) images show spherical cubic microcrystals in the samples. EDX analysis confirms that the synthesized ferrite is pure phase structure, and Mg{sup 2+} is successfully replaced. With the increase of Mg{sup 2+} ion content, the saturation magnetization and remanent magnetization decreased from 70.16 to 39.77 emu/g and 36.40 to 20.20 emu/g at room temperature, respectively. Meanwhile, the coercivity decreases from 1032.16 to 378.50 Oe by increasing Mg{sup 2+} concentration. This also indicates that the Mg-substituted Ni-Co nano-ferrite has a low magnetic of multi-ferric material. The increasing of peak height of dM/dH at H{sub m} indicates that the cubic spinel structure sample has good crystallinity and magnetic stability.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Ab Initio Investigation of Structural, Electronic, and Magnetic Properties of Cr-Doped ZnS and ZnSe in Wurtzite Structure
Using the first-principles calculations with the full potential linear muffin–tin orbital (FP-LMTO) method, we investigated the structural, electronic, and magnetic properties of Zn{sub 1−x}Cr{sub x}(S,Se)-diluted magnetic semiconductors (DMSs) in wurtzite structures with varying concentrations (x = 0.0625, x = 0.125, and x = 0.25) of Cr. The electronic properties indicated that Zn{sub 1−x}Cr{sub x}(S,Se), in all concentrations, exhibited half-metallic ferromagnetic (HMF) behavior with spin polarization of 100%. The density of states showed a hybridization between the p(S, Se) and 3d(Cr) states, which created an antibonding state in the gap that stabilized the ferromagnetic ground state linked to the double-exchange mechanism. Therefore, these compounds are highly likely candidates for spintronic applications.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Electronic and Magnetic Properties of Oligomers and Chains of Poly(benzodifurandione) (PBDF), A Highly Conducting n-Type Polymer
The seminal development of highly electrically conducting polyacetylene via oxidative or reductive treatment (“doping”) has continuously inspired the search for other conducting π-conjugated polymers. Recently, poly(benzodifurandione), PBDF, was reported to have unexpected solubility given the absence of side chains and to exhibit an unprecedented, high electrical conductivity upon reduction (“n-doping”), with protons acting as counterions. Here, we theoretically investigate the electronic and magnetic properties of PBDF by taking long oligomers and one-dimensional (1D) periodic chains as model systems. With the oligomer models, we characterize the formation of polarons and bipolarons in n-doped PBDF. Our results indicate that singlet bipolarons tend to be the energetically most favorable species when protons bind to two closely located carbonyl groups in nearest-neighbor benzodifurandione moieties. The calculations on the 1D periodic chain models show that the positions of the protonated carbonyl groups determine the metallic, semiconducting, or insulating nature of a PBDF chain. When the protonated carbonyl groups are all situated on the same side of a PBDF chain, a stable helical chain configuration is found that exhibits ferromagnetic behavior. Our findings elucidate the mechanism of polaron and bipolaron formation in long oligomers of n-doped PBDF and highlight the fascinating electronic and magnetic properties of periodic 1D chains. Furthermore, these studies also provide a stepping stone for investigations of PBDF thin films, for which two- and three-dimensional structures must be considered.
36 MATERIALS SCIENCE↗
Enhancement in hard magnetic properties of (Nd, Pr)–Fe–B melt-spun ribbons
The coercivity of RE 2 Fe 14 B-type permanent magnets is strongly influenced by the microstructural features such as grain boundary (GB) phases as well as grain sizes. Here, we have combined micromagnetic simulations and experiments to elucidate the role of excess RE (Nd/Pr) in determining the resulting hard magnetic properties of Nd–Pr–Fe–B melt-spun ribbons. The intrinsic coercivity (H c ) at room temperature significantly enhanced from 9.7 kOe to 15.3 kOe with the increase in the Nd/Pr content. Furthermore, the effect of non-magnetic grain refining refractory carbide (TiC) on both the microstructure and magnetic hardening was studied. The addition of TiC showed a very high coercivity H c of up to 19.0 kOe at room temperature. Micromagnetic simulation indicates that the coercivity enhancement is mainly due to the reduction of inter-grain magnetic interaction, which is due to the RE-rich nonmagnetic grain boundary (GB) phase and/or TiC distributed at the GB. This work provides useful information on the roles of non-magnetic grain boundary phases for improving the coercivity of Nd–Pr–Fe–B magnets. Combined with experimental and modeling results, we have discussed the mechanism responsible for the enhancements in coercivity and the suitability of the alloys for high-performance permanent magnet development.
36 MATERIALS SCIENCE↗
Microstructure and Magnetic Properties of Ba{sub 0.95}Y{sub 0.05}Fe{sub 12−x}Co{sub x}O{sub 19} Hexaferrites
Magnetoplumbite-type (M-type) barium ferrites doped with different Y–Co doping content Ba{sub 0.95}Y{sub 0.05}Fe{sub 12−x}Co{sub x}O{sub 19} (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) were successfully prepared by ceramic process and investigated in this paper for the first time. X-ray diffraction were used to analyze the phase of the prepared sample. The scanning electron microscopy (SEM) was used to measure the morphology, and magnetic properties were measured by vibrating sample magnetometer (VSM). The results of XRD show that the single phase of M-type barium ferrites was obtained with the increase of Co content (x), but α-Fe{sub 2}O{sub 3} occurred when x exceeds 0.3. The SEM results exhibit the uniform plane hexagonal structures of M-type ferrites with all range of Co doping content. VSM results display that magnetization (M{sub s}) and coercivity (H{sub c}) show the same tendency that their values first increase and then decrease with the increase of Co content.
36 MATERIALS SCIENCE↗
Effect of Intrinsic Defects on Electronic and Magnetic Properties in Tm-Doped GaN: First-Principles Calculations
Based on the density functional theory, we investigate the electronic and magnetic properties of various types of defect complexes formed by dopant Tm and Ga vacancies, N vacancies, or O interstitial in Tm-doped GaN. Formation energies are first calculated for all defect complexes to assess their stability. The single Tm dopant is found to introduce the local magnetic moment of about 2 μ{sub B}/Tm in GaN. However, in the case of defect complexes, the magnetic moments of Tm can be suppressed by the existence of Ga vacancies around it, while the presence of N vacancies or O interstitial does not influence the magnetic moment of Tm. In addition, each Ga vacancy in the neutral charge state induces the local magnetic moment of about 2.1 μ{sub B} and one octahedral O interstitial can lead to the local moment of about 1.6 μ{sub B}.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗