•Bulk disk shaped Sm2Fe17Nx magnets were obtained by the high pressure torsion method.•The maximum coercivity Hc = 624.4 kA/m was achieved after 3 turns.•HPT of Sm2Fe17Nx alloy at room temperature is ...equivalent to annealing at T = 1000 K.
In this study the structure and magnetic properties of Sm2Fe17Nx alloys after high pressure torsion (HPT) was investigated. As a result of HPT, bulk samples were obtained as disk-shaped 0.5 mm high and 8 mm in diameter. The maximum coercivity Hc = 621.4 kA/m (7.7 kOe) was obtained on the samples after 3 turns (e = 5.01) with the remanence magnetization σr = 57.7A·m2/kg. It was shown that HPT leads to decomposition of the Sm2Fe17Nx phase with the formation of α-Fe and the exchange-coupled state. The influence of temperature on the deformation processes of Sm2Fe17Nx alloys was established.
Neodymium iron boron (NdFeB) magnets are sintered anisotropic materials. They were commercially introduced in the early 1980s, and since have been used in different applications owing to their ...superior properties. Herein, we investigated the influence of 0.5 to 8 h of milling time on the morphological, structural, and magnetic performance of Nd _9.6 Fe _80.3 Zr _3.7 B _6.4 powders produced using surfactant-assisted high-energy ball milling (SA-HEBM). The results revealed that the relationship between coercivity ( H _ci ) and milling time had a non-monotonous character reaching a maximum value of H _ci = 8.92 kOe after 1 h of milling. The effect of the volume ratio of various magnetic phases (Nd _2 Fe _14 B and α -Fe) on microstructure and magnetic properties was also reported. The highest specific saturation magnetization ( σ _s = 120 emu g ^−1 ) was attained after 8 h of milling for powders with volume fraction: Nd _2 Fe _14 B–81 ± 2% and α -Fe–12 ± 2%. The expected value of Nd _2 Fe _14 B specific saturation magnetization was estimated ( σ _N = 108 ± 2.5 emu g ^−1 ) using the experimental value of σ _s and magnetic phase volume fractions. The ratio of remanence to saturation magnetization of the Nd _2 Fe _14 B with milling time was also determined and analyzed.
This paper investigates complex studies of phase composition, thin crystalline structure parameters and magnetic properties of rapidly solidified alloy powders Nd10.4Zr4.0Fe75.1Co4.1B6.4 in initial ...state and after heat treatments in the temperature range 380–700 °C for 30, 60 and 120 min. The research shows that there is a hard magnetic phase Nd2Fe14B and soft magnetic phases α-Fe and Nd2Fe17 in the structure of the investigated as-solidified alloy. And low-magnetic properties (Hci = 186 kA/m) are due to the presence of the Nd2Fe17 phase. After heat treatments in the temperature range 520–550 °C coercivity of the powders grow up to Hci ≈ 750 kA/m. However, after annealing at the temperatures higher than 600 °C, coercivity drastically drops due to the phase transformation of a hard magnetic phase Nd2Fe14B and the average grain growth, with the phase transforming into a soft magnetic phase Nd2Fe17.
•Investigated phase transformation and magnetic properties in Nd10.4Zr4.0FeCo4.1B6.4.•After annealing at 520–550 °C and coercivity increases up to 700–750 kA/m.•After annealing at >560 °C a transformation of Nd2Fe14B into Nd2Fe17 phase occurs.
Nonmonotonic variation with collision energy (sqrts_{NN}) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of ...the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of sqrts_{NN} with 3.1 σ significance for head-on (central) gold-on-gold (Au+Au) collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral Au+Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of sqrts_{NN}.
The influence exerted by specific synthesis protocol conditions on the crystal, local atomic and electronic structures of various types of Ce chromates/chromites prepared by the coprecipitation is ...studied using synchrotron X-ray diffraction, X-ray absorption fine structure (XAFS), Raman and Fourier transform infrared (FT-IR) spectroscopies, and simultaneous thermal analysis. Cerium chromate heptahydrate Ce2+3(Cr+6O4)3(H2O)5⋅2H2O with the monoclinic structure (sp. gr. P21/c) has been synthesized and characterized structurally for the first time.
It has been established that calcination of all types of precursors in air at a temperature ≥ 450 °C leads to the formation of a mixture of CeO2 and Cr2O3 phases. The calcination in vacuum at 1200 °C affords CeCrO3 (with the orthorhombic structure, sp. gr. Pnma(62)), which upon repeated heating to above 650–700 °C in air tends to decompose into CeO2 and Cr2O3 phases. Long-range XRD data correlate well with the results of techniques sensitive to the local structure parameters, such as XAFS, Raman and FT-IR. XANES spectra measured at the Cr K- and Ce L3- edges strongly imply that the synthesis procedures are accompanied by concerted redox transformations Cr6+→ Cr3＋ and Ce3+⟷ Ce4+.
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•The crystal, local and electronic structures of Ce chromates/chromites are studied.•A combination of s-XRD, XANES, Raman and FT-IR, STA techniques is applied.•Ce2+3(Cr+6O4)3⋅7H2O (monoclinic, P21/c) has been synthesized for the first time.•Vacuum calcination at 1200 °C affords CeCrO3 (orthorhombic, Pnma).•The synthesis is accompanied by concerted redox reactions Cr6+→ Cr3+ and Ce3+⟷ Ce4+.
The Breit-Wheeler process which produces matter and antimatter from photon collisions is experimentally investigated through the observation of 6085 exclusive electron-positron pairs in ...ultraperipheral Au + Au collisions at √sNN = 200 GeV . The measurements reveal a large fourth-order angular modulation of cos 4 Δ ϕ = ( 16.8 ± 2.5 ) % and smooth invariant mass distribution absent of vector mesons ( ϕ , ω , and ρ ) at the experimental limit of ≤ 0.2 % of the observed yields. The differential cross section as a function of e+ e− pair transverse momentum P⊥ peaks at low value with √⟨P⊥2 ⟩ = 38.1 ± 0.9 MeV and displays a significant centrality dependence. These features are consistent with QED calculations for the collision of linearly polarized photons quantized from the extremely strong electromagnetic fields generated by the highly charged Au nuclei at ultrarelativistic speed. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.
We report the first measurements of the moments--mean (M), variance (σ(2)), skewness (S), and kurtosis (κ)--of the net-charge multiplicity distributions at midrapidity in Au+Au collisions at seven ...energies, ranging from sqrtsNN=7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, σ(2)/M, Sσ, and κσ(2), with the expectations from Poisson and negative binomial distributions (NBDs). The Sσ values deviate from the Poisson baseline and are close to the NBD baseline, while the κσ(2) values tend to lie between the two. Within the present uncertainties, our data do not show nonmonotonic behavior as a function of collision energy. These measurements provide a valuable tool to extract the freeze-out parameters in heavy-ion collisions by comparing with theoretical models.
We report the beam energy (sqrtsNN=7.7-200 GeV) and collision centrality dependence of the mean (M), standard deviation (σ), skewness (S), and kurtosis (κ) of the net-proton multiplicity ...distributions in Au+Au collisions. The measurements are carried out by the STAR experiment at midrapidity (|y|<0.5) and within the transverse momentum range 0.4<pT<0.8 GeV/c in the first phase of the Beam Energy Scan program at the Relativistic Heavy Ion Collider. These measurements are important for understanding the quantum chromodynamic phase diagram. The products of the moments, Sσ and κσ2, are sensitive to the correlation length of the hot and dense medium created in the collisions and are related to the ratios of baryon number susceptibilities of corresponding orders. The products of moments are found to have values significantly below the Skellam expectation and close to expectations based on independent proton and antiproton production. The measurements are compared to a transport model calculation to understand the effect of acceptance and baryon number conservation and also to a hadron resonance gas model.
Comprehensive studies of powders with a nominal composition of 90% 43% Fe
2
O
3
–57% FeO–10% Gd
2
O
3
are performed via scanning electron microscopy, microscopic X-ray spectral and phase analysis, ...differential scanning calorimetry, and measuring hysteresis properties. It is shown that the main phases in the powders after high-energy ball milling are magnetite (Fe
3
O
4
) and an amorphous phase; in addition, the powders contain about 2 vol % wustite (FeO) and less than 1 vol % orthoferrite (GdFeO
3
). Trends of changes in the phase composition, structure, and hysteresis properties of the annealed powders are identified.
Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge ...separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies.
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