Ordering Of Nd Research Articles

IR magnetotransmission in double NdBaMn<sub>2</sub>O<sub>6</sub> manganite with different degrees of ordering in A-position

The structural, magnetic, and optical properties of double manganites NdBaMn2O6 have been studied depending on the degree of ordering of Nd and Ba atoms in the A-position. Analysis of temperature dependences of light transmission shows the changes of charge carrier subsystem in vicinity of structural and magnetic phase transitions. When the metal-insulator transition occurs the effect of light magnetotransmission near Curie temperature was found.

Negative magnetization and magnetic ordering of rare earth and transition metal sublattices in NdFe0.5Cr0.5O3

We investigate the effect of alloying at the 3d transition metal site of a rare-earth-transition metal oxide, by considering NdFe0.5Cr0.5O3 mixed perovskite with two equal and random distribution of 3d ions, Cr and Fe, interacting with an early 4f rare earth ion, Nd. Employing temperature- and field- dependent magnetization measurements, temperature-dependent x-ray diffraction, neutron powder diffraction, and Raman spectroscopy, we characterize its structural and magnetic properties. Our study reveals bipolar magnetic switching (arising from negative magnetization) and magnetocaloric effect which underline the potential of the studied mixed perovskite in device application. The neutron diffraction study shows the absence of spin reorientation transition over the entire temperature range of 1.5–320 K, although both parent compounds exhibit spin orientation transition. We discuss the microscopic origin of this curious behavior. The neutron diffraction results also reveal the ordering of Nd spins at an unusually high temperature of about 40 K, which is corroborated by Raman measurements.

Magnetization reversal, critical behavior, and magnetocaloric effect in NdMnO3: The role of magnetic ordering of Nd and Mn moments

The magnetic properties, critical behavior, and magnetocaloric effect of perovskite NdMnO3 are studied. The Nd ordering is induced by the Mn ferromagnetic component with antiferromagnetic coupling with each other and then magnetization reversal occurs due to Mn moments reorientation induced by the ordering Nd moments, which explains the phenomenon of negative magnetization at low temperatures. The critical behavior of NdMnO3 is studied using Kouvel–Fisher and self-consistent methods. The results show that the Kouvel–Fisher method is reliable and critical exponents are coming out as β = 0.462 for TC = 11.15 K, γ = 1.041 for TC = 11.42 K, δ = 3.252 by critical isotherm analysis. Magnetic exchange distance may decay as J(r)≈r−4.563, that is, somewhere between the three-dimensional Heisenberg model and the mean field model. Remarkably, three temperature transitions and the corresponding three extremum values including positive and negative entropy change are observed in NdMnO3, which is different from previous reports on NdMnO3. A positive entropy change as 3.82 J/kg K at 10–15 K for μ0ΔH = 50 kOe and a negative entropy change as −0.557 J/kg K at around 8 K for μ0ΔH = 5 kOe are found, which can be put down to a fast magnetization change of NdMnO3 because of the Nd moments ordering and Mn moments reorientation. Besides, an entropy change of 1.22 J/kg K is found for μ0ΔH = 50 kOe at 80–85 K, which is corresponding to the Mn ferromagnetic ordering temperature. The relative cooling power of NdMnO3 reaches 105.9 J/kg, making it a promising candidate in the field of magnetic refrigeration.

Order out of a Coulomb Phase and Higgs Transition: Frustrated Transverse Interactions of Nd_{2}Zr_{2}O_{7}.

The pyrochlore material Nd_{2}Zr_{2}O_{7} with an "all-in-all-out" (AIAO) magnetic order shows novel quantum moment fragmentation with gapped flat dynamical spin ice modes. The parametrized spin Hamiltonian with a dominant frustrated ferromagnetic transverse term reveals a proximity to a U(1) spin liquid. Here we study the magnetic excitations of Nd_{2}Zr_{2}O_{7} above the ordering temperature (T_{N}) using high-energy-resolution inelastic neutron scattering. We find strong spin ice correlations at zero energy with the disappearance of gapped magnon excitations of the AIAO order. It seems that the gap to the dynamical spin ice closes above T_{N} and the system enters a quantum spin ice state competing with and suppressing the AIAO order. Classical MonteCarlo simulations, molecular dynamics, and quantum boson calculations support the existence of a Coulombic phase above T_{N}. Our findings relate the magnetic ordering of Nd_{2}Zr_{2}O_{7} with the Higgs mechanism and provide explanations for several previously reported experimental features.

Tailoring the ferrimagnetic-to-ferromagnetic transition field by interstitial and substitutional atoms in the R–Fe compounds

Fundamental characteristics of rare-earth (R) – iron intermetallics R2Fe14B are highly sensitive to the atomic substitutions and interstitial absorption of light elements. We studied a combined influence of the substitutions in the rare-earth sublattice and hydrogen absorption on the magnetization behavior in magnetic fields up to 60 T Er2Fe14B and Tm2Fe14B ferrimagnets chosen for the study showed that the substitution of Nd for Er or Tm increases the saturation magnetization as a result of ferromagnetic ordering of Nd and Fe moments. Under sufficiently high magnetic fields the magnetic moments rotate and the field-induced ferromagnetic state may be observed. The field at which a transition occurs is related to the strength of the inter-sublattice exchange interaction. The role of hydrogen is primarily to weaken the inter-sublattice ferrimagnetic coupling so that the reorientation becomes achievable at the available magnetic field strength (in hydrides Tm2Fe14BH5.5 and (Tm0.5Nd0.5)2Fe14BH5.5). We analyze the volume dependence of the R–Fe magnetic interaction in R2Fe14B and compare it with other R–Fe compounds.

Complexation of Lanthanides with N, N, N', N'-Tetramethylamide Derivatives of Bipyridinedicarboxylic Acid and Phenanthrolinedicarboxylic Acid: Thermodynamics and Coordination Modes.

The thermodynamics of Nd(III) and Eu(III) complexes with N, N, N', N'-tetramethyl-2,2'-bipyridine-6,6'-dicarboxamide (TMBiPDA) and N, N, N', N'-tetramethyl-1,10-phenanthroline-2,9-dicarboxamide (TMPhenDA) in CH3OH/10%(v)H2O solutions were studied. Stability constants and enthalpies of complexation were determined by absorption spectrophotometry, luminescence, and calorimetry. The stability constants of corresponding lanthanide complexes decrease in the order of TMPhenDA > TMBiPDA, while those of the corresponding ligand complexes with lanthanides decrease in the order of Nd(III) > Eu(III). The stepwise reactions for all 1:1 complexes as well as for the 1:2 Nd(III) complexes are driven by both enthalpy and entropy, while those for the 1:2 Eu(III) complexes are driven by entropy. The stronger affinity of TMPhenDA to Nd(III) and Eu(III) than that of TMBiPDA is predominantly arisen from its high preorganization. The spectra of the complexes in solutions are similar, implying that Nd(III) and Eu(III) coordinate with the two ligands in the same mode, which have been validated by 1H and 13C NMR titrations using La(III) as lanthanide tracer. The luminescence lifetimes of the Eu(III) complexes with TMBiPDA and TMPhenDA were evaluated by TRLFS. Structures of Nd(III)/TMPhenDA and Eu(III)/TMPhenDA complexes, identified by single-crystal X-ray diffractometry, show that ligand coordinates to metal in a tetradentate mode via two aromatic N-donors and two amide O-donors, and the central cation (Nd(III) or Eu(III)) is 10-coordinated by two whole TMPhenDA and two solvent (water or methanol) molecules. The M-O bond distances are almost identical, while the Nd-N bond distance is shorter than the Eu-O bond.

Microstructural and mechanical anisotropy of extruded in-situ TiB2/2024 composite plate

The influence of crystallographic texture, grain shape and TiB2 particle distribution on the mechanical anisotropy with respect to three-dimensional directions of in-situ TiB2/2024 composite plate has been investigated. The grains of the composite are strongly elongated along extrusion direction (ED). Most of TiB2 particles are aligned along the long grain axis in both ED-TD (TD: transverse direction) and ED-ND (ND: normal direction) planes to form the particle bands. In the concerned three directions, the yield/ultimate tensile strength and elongation are all increasing in the directional sequence of ND<TD<ED, signifying both the strength and ductility anisotropic behaviors have existed in the composite plate. For the fracture behavior, the composite specimen along ED shows the ductile fracture. In comparison, the composite specimens along ND and TD show the brittle fracture. Regarding the strength anisotropy, the texture component and texture factor are adopted to analyze. It is found that the average texture factor has a directional order of ND<TD<ED, which is the major cause to the strength anisotropy. For the ductility anisotropy, the grain shape and TiB2 particle distribution factors are included in the analysis. Notably, the fracture paths are always along TiB2 particle bands and elongated grains, which are the primary sources of the ductility loss in TD and ND.

Epitaxial growth of iridate pyrochlore Nd2Ir2O7 films.

Epitaxial films of the pyrochlore Nd2Ir2O7 have been grown on (111)-oriented yttria-stabilized zirconia (YSZ) substrates by off-axis sputtering followed by post-growth annealing. X-ray diffraction (XRD) results demonstrate phase-pure epitaxial growth of the pyrochlore films on YSZ. Scanning transmission electron microscopy (STEM) investigation of an Nd2Ir2O7 film with a short post-annealing provides insight into the mechanism for crystallization of Nd2Ir2O7 during the post-annealing process. STEM images reveal clear pyrochlore ordering of Nd and Ir in the films. The epitaxial relationship between the YSZ and Nd2Ir2O7 is observed clearly while some interfacial regions show a thin region with polycrystalline Ir nanocrystals.

Effect of ultrasonic cavitation on the diffusivity of a point defect in the passive film on formed Nb in 0.5 M HCl solution

This work primarily focused on the influence of ultrasonic cavitation on the transport property of the point defect in the passive film on formed Nb in 0.5M HCl solution via electrochemical techniques based on the point defect model (PDM). The influence of ultrasonic cavitation on the composition and structure of the passive film was detected by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The transport property of a point defect in the passive film was characterized by the diffusivity of the point defect (D0). The influences of the ultrasonic cavitation power, passivated time and the distance between horn bottom and sample surface on D0 were analyzed. The results demonstrated that the passive film formed on Nb was an n-type semiconductor with a donor density (ND) ranging from 1019cm−3 to 1020cm−3 in the case of static state, while the order of ND increased one to two times by applying ultrasonic cavitation during film formation. The diffusivity of the point defect (D0) in the passive film formed on Nb at 0.5V for 1h in a 0.5M HCl solution in the static state was calculated to be 9.704×10−18cm2s−1, and it increased to 1.255×10−16cm2s−1, 7.259×10−16cm2s−1 and 7.296×10−15cm2s−1 when applying the 180W, 270W and 450W ultrasonic cavitation powers during film formation. D0 increased with the increment of the ultrasonic cavitation power, and decreased with the increased in formation time and distance between the horn bottom and sample surface. AES results showed the film structure and composition were changed by applying the ultrasonic cavitation. XPS results revealed that the passive film was mainly composed of Nb2O5 in the static state, and the low valence Nb-oxide (NbO) appeared in the passive film except Nb2O5 in the case of applying a 270W ultrasonic cavitation power.

Unconventional magnetism in ThCr2Si2-type phosphides, La1−xNdxCo2P2

Quaternary phases La1−xNdxCo2P2 (x = 0, 0.12, 0.25, 0.37, 0.50, 0.63, 0.75, 0.88, 1.0) have been synthesized from Sn flux to investigate the origins of drastic differences in properties between ferromagnetic LaCo2P2 and antiferromagnetic NdCo2P2. Powder and single-crystal X-ray diffraction indicate that all La1−xNdxCo2P2 samples are isostructural and crystallize in the ThCr2Si2 structure type. The unit cell parameters and volume change non-linearly with the Nd content (x), with the x 0.50 being closer to NdCo2P2. These structural differences are also reflected in the magnetic behavior. The samples with lower Nd content are characterized by ferromagnetic ordering in the Co sublattice with the TC increasing from 132 K for x = 0 to 262 K for x = 0.50, while the samples with higher Nd content exhibit suppressed magnetization in the Co sublattice and canted antiferromagnetic ordering with TC ∼ 270 K. Refinement of neutron powder diffraction patterns for x = 0.50 and 0.75 reveals a gradual ordering of the Nd 4f moments under the influence of Co 3d moments below 100 K. At low temperatures and zero field, these samples exhibit antiferromagnetic ordering of both Nd and Co magnetic moments, but under applied field they demonstrate the stabilization of a ferrimagnetic state with antiparallel alignment of the 4f and 3d moments, as indicated by isothermal magnetization measurements. The re-entrant ferrimagnetic transition is also observed in samples with x > 0.50 if the temperature is lowered below 5 K. The occurrence of this low-temperature magnetic transition was confirmed by alternating-current susceptibility measurements.

Steric effect involved in Ln3+/Ce3+exchange in a coordination polymer based on di(2-ethylhexyl)phosphoric acid

Coordination polymers can be attractive ion exchange materials because of their crystallinity and semi-flexibility, which are rather opposing properties, and play integral and synergistic roles in introducing unique ion-exchange behavior. In this paper, Ln(3+)/Ce(3+) exchange (Ln(3+) = Nd(3+), Gd(3+), Dy(3+), or Lu(3+)) in a coordination polymer, [Ce(dehp)3], based on di(2-ethylhexyl)phosphoric acid (Hdehp) is studied by distribution coefficient measurements, ion-exchange isotherms, Kielland plot analysis, and morphology observation. The ion-exchange selectivity is in the order Nd(3+) < Gd(3+) < Dy(3+) < Lu(3+) when a small amount of Ln(3+) is loaded, but Lu(3+) ≈ Nd(3+) < Gd(3+) ≈ Dy(3+) for a high loading ratio. The Kielland plot suggests that a steric effect is involved in the reactions, which becomes stronger in the order of Nd(3+)/Ce(3+) < Gd(3+)/Ce(3+) < Dy(3+)/Ce(3+) < Lu(3+)/Ce(3+) for exchange systems. This trend is attributable to the differences in the ionic sizes between an incoming Ln(3+) and original Ce(3+). Scanning electron microscopy observations reveal the generation of a new phase via the Ln(3+)/Ce(3+) exchange. Such a phenomena results from solid-solid transformation, rather than dissolution-recrystallization. The small steric strain in the Nd(3+)/Ce(3+) system leads to the formation of a Nd(3+)-and-Ce(3+) solid-solution, whereas the morphological change is possibly restrained by the strong strain caused by loaded Ln(3+) with an ionic size significantly smaller than the original Ce(3+).

Magnetic order in the pyrochlore iridate Nd2Ir2O7probed by muon spin relaxation

Muon spin relaxation results on the pyrochlore iridate Nd${}_{2}$Ir${}_{2}$O${}_{7}$ are reported. Spontaneous coherent muon spin precession below the metal-insulator transition (MIT) temperature of about 33 K is observed, indicating the appearance of a long-range magnetic ordering of Ir${}^{4+}$ moments. With further decrease in temperature, the internal field at the muon site increases again below about 9 K. The second increase of internal field suggests the ordering of Nd${}^{3+}$ moments, which is consistent with a previous neutron experiment. Our results suggest that the MIT and magnetic ordering of Ir${}^{4+}$ moments have a close relationship and that the large spin-orbit coupling of Ir 5$d$ electrons plays a key role for both MIT and the mechanism of the magnetic ordering in pyrochlore iridates in the insulting ground state.

Origin of anomalous octahedral distortions and collapse of magnetic ordering in Nd1−xSrxFeO3 (0≤x≤0.5)

The effects of strontium doping on the structural properties and magnetic ordering of Nd 1− x Sr x FeO 3 orthoferrite system have been studied by employing macroscopic and microscopic structural techniques like X-ray diffraction, scanning electron microscopy and 57 Fe Mössbauer spectroscopy. X-ray diffraction confirmed that single phase materials have been synthesized. It has been observed that orthorhombic distortion, density and porosity have decreased; whereas, grain size, tolerance factor and symmetry have increased with increase in the strontium concentration. Mössbauer results showed an increase in the Fe 4+ /Fe 3+ ratio, sagging and local octahedral distortions while decrease in the magnetic ordering with increase in the strontium content. The origin behind anomalous octahedral distortions in this system has been attributed to the decrease in the oxidation state and mismatch in the ionic radii of A-site cations and increase in the concentration of Fe 4+ , due to Sr 2+ doping at Nd 3+ sites. The collapse of magnetic ordering has been ascribed to the weakening of super-exchange interactions, dilution of strong long range magnetic sub-lattice of high spin Fe 3+ (five unpaired electrons) by relatively lower spin of high spin Fe 4+ (four unpaired electrons) and increase in the spin–spin relaxation frequency.

Smoothed rank correlation of the linear transformation regression model

The maximum rank correlation (MRC) approach is the most common method used in the literature to estimate the regression coefficients in the semiparametric linear transformation regression model. However, the objective function Gn(β) in the MRC approach is not continuous. The optimization of Gn(β) requires an extensive search for which the computational cost grows in the order of nd, where d is the dimension of X. Given the lack of smoothing, issues related to variable selection, the variance estimate and other inferences by MRC are not well developed in the model. In this paper, we combine the concept underlying the penalized method, rank correlation and smoothing technique and propose a nonconcave penalized smoothed rank correlation method to select variables and estimate parameters for the semiparametric linear transformation model. The proposed estimator is computationally simple, n1/2−consistent and asymptotically normal. A sandwich formula is proposed to estimate the variances of the proposed estimates. We also illustrate the usefulness of the methodology with real data from a body fat prediction study.

Magnetic transitions and magnetodielectric effect in antiferromagnet SrNdFeO4

We investigated the magnetic phase diagram of single crystals of SrNdFeO$_{4}$ by measuring the magnetic properties, the specific heat and the dielectric permittivity. The system has two magnetically active ions, Fe$^{3+}$ and Nd$^{3+}$. The Fe$^{3+}$ spins are antiferromagnetically ordered below 360 K with the moments lying in the ab-plane, and undergo a reorientation transition at about 35-37 K to an antiferromagnetic order with the moments along the c-axis. A short-range, antiferromagnetic ordering of Nd$^{3+}$ along the c-axis was attributed to the reorientation of Fe$^{3+}$ followed by a long-range ordering at lower temperature [S. Oyama {\it et al.} J. Phys.: Condens. Matter. {\bf 16}, 1823 (2004)]. At low temperatures and magnetic fields above 8 T, the Nd$^{3+}$ moments are completely spin-polarized. The dielectric permittivity also shows anomalies associated with spin configuration changes, indicating that this compound has considerable coupling between spin and lattice. A possible magnetic structure is proposed to explain the results.

Physical property characterization of single step synthesized NdFeAsO0.80F0.20 bulk 50 K superconductor

We report an easy single step synthesis route of title compound NdFeAsO0.80F0.20 superconductor having bulk superconductivity below 50 K. The title compound is synthesized via solid-state reaction route by encapsulation in an evacuated (10-3 Torr) quartz tube. Rietveld analysis of powder X-ray diffraction data shows that compound crystallized in tetragonal structure with space group P4/nmm. R(T)H measurements showed superconductivity with T c (R = 0) at 48 K and a very high upper critical field (H c2) of up to 345 T. Magnetic measurements exhibited bulk superconductivity in terms of diamagnetic onset below 50 K. The lower critical field (H c1) is around 1000 Oe at 5 K. In normal state i.e., above 60 K, the compound exhibited purely paramagnetic behavior and thus ruling out the presence of any ordered FeO x impurity in the matrix. In specific heat measurements a jump is observed in the vicinity of superconducting transition (T c ) along with an upturn at below T = 4 K due to the AFM ordering of Nd+3 ions in the system. The Thermo-electric power (TEP) is negative down to T c , thus indicating dominant carriers to be of n-type in NdFeAsO0.80F0.20 superconductor. The granularity of the bulk superconducting NdFeAsO0.8F0.2 sample is investigated and the intra and inter grain contributions have been individuated by looking at various amplitude and frequencies of the applied AC drive magnetic field.

Glassy behavior of the Nd sublattice induced by Fe doping in [formula omitted

The evolution of the magnetic ordering of Nd with the Fe content in NdFe x Ga 1 - x O 3 is studied by low-temperature specific-heat measurements for x ⩽ 0.2 . The experiments show that Nd ordering takes place for x ⩽ 0.1 , but it is inhibited for x ⩾ 0.2 . Fe doping creates a distribution of internal fields on Nd, originating a Schottky contribution to the specific heat which is present for x > 0 . The power law followed by the low-temperature specific heat suggests a glassy behavior for x ⩾ 0.1 .

Effect of rare-earth-site cations on the physical properties ofLa0.7−yNdyPb0.3MnO3single crystals

Single crystals of $La_{0.7–-y}Nd_yPb_{0.3}MnO_3$ with different y are grown by flux growth technique. The influence of change in average cationic radius $(\langle r_A\rangle)$ and cation size disorder $(\sigma^2)$ on the transport and magnetic properties of these crystals due to the presence of different cations (La and Nd) on the rare-earth sRd site is studied. Curie temperature $T_C$ and metal-insulator transition temperature $T_M_I$ are sensitive to the R site occupation. The temperature dependence of magnetization of $La_{0.7}Nd_yPb_{0.3}MnO_3$ is consistent with spin wave excitations according to the Bloch $T^{3/2}$ law at zero magnetic field limit. The Nd-based systems follow $T^{3/2}$ law only in a certain range of temperature and deviate at low temperatures, which is ascribed to a probably canted ordering of Nd and Mn moments with an antiferromagnetic component at very low temperatures. The values of spin stiffness constants and saturation magnetization vary systematically with changing occupation on the R site. Specific heat measurements of Nd containing samples show a Schottky-like anomaly at low temperature (below 15 K), which increases with the concentration of Nd ions in the lattice. It is concluded that the magnetic properties of manganites with Nd are affected by a tendency for magnetic ordering of the Nd ions.

Temperature and field dependence of the magnetic properties of Nd $\mathsf{_{2-x}}$ Ce $\mathsf{_{x}}$ CuO $\mathsf{_4}$

We have investigated the magnetic ordering of Nd2-x Ce x CuO4 for x = 0, 0.09, 0.13, 0.15 and 0.18 by neutron diffraction at low temperatures down to 33 mK and under magnetic field up to 5 tesla applied along [1,-1,0] crystallographic direction. At zero applied magnetic field Cu magnetic sublattice orders at $T_{N} \approx 250$ , 210, 130 and 105 K for x = 0, 0.09, 0.13, 0.15, respectively. No long range magnetic order of the Cu could be detected for x = 0.18. The magnetic order of Nd was found in all samples, with a gradual increase of the polarized magnetic moment with decreasing temperature, saturating around 1 K. Hyperfine induced nuclear polarization of the Nd nuclear spin has been observed below about 400 mK for samples with x = 0, 0.13, 0.15 and 0.18. Field variation of the intensities of the principal and superstructure reflections of Nd2-x Ce x CuO4 at millikelvin temperatures shows a field-induced second-order double-k to single-k phase transition at H c = 0.75 and 0.56 tesla for samples with x = 0 and 0.15, respectively at T = 50 mK. We have also investigated the polarization of the Nd electronic sublattice due to the field of the Cu sublattice by the element specific X-ray resonant magnetic scattering investigation with synchrotron radiation.

Electrophilic Aromatic Substitutions of Amine and Sulfonate onto Fine-Grained Activated Carbon for Aqueous-Phase Metal Ion Removal

ABSTRACTTwo new materials for adsorption of metal ions from aqueous media have been developed. The organic functional groups amine (−NH2) and sulfonate (−SO3H) were successfully attached to a commercially available fine-grained activated carbon (AC) via electrophilic aromatic substitutions. The surface properties of the materials were investigated using FTIR spectroscopy, XPS, BET surface area analysis, gravimetric methods, and elemental analysis. The NH2-AC and SO3H-AC each had a functional group density of 3 mmol/g. Batch metal ion adsorption experiments were conducted to determine metal binding properties of the adsorbent materials. Based on the distribution coefficients (Kd) of metal ions tested, the unmodified AC and sulfonated-AC both had an affinity for metal ions in decreasing order of Nd > Lu ≈ La > Pb > Cu > Ni ≈ Cd > Mn ≈ Ca, while the amine-AC had an affinity for metal ions in the order of Cu ≫ Nd ≈ Lu ≈ La > Pb > Ni > Cd > Mn ≈ Ca. With maximum Kd values of 130,000 for amine-AC and 25,000 for sulfonated-AC, compared to a Kd of 2,000 for unmodified AC, the modified activated carbons have a strong potential for use in removing heavy metal ions and lanthanide ions from aqueous wastes.