Transport Properties Of Nd0 Research Articles

Study of Dielectric Relaxation Dynamics and Transport Properties of Nd3+-Substituted Bismuth Ferrite Ceramics for Energy Storage Applications

Study of Dielectric Relaxation Dynamics and Transport Properties of Nd³⁺-Substituted Bismuth Ferrite Ceramics for Energy Storage Applications

Improved temperature coefficient of resistance and transport properties of Nd0.7Sr0.3−xAxMnO3 (A = Ag, Na, K: x = 0 & 0.1) manganites

Improved temperature coefficient of resistance and transport properties of Nd0.7Sr0.3−xAxMnO3 (A = Ag, Na, K: x = 0 & 0.1) manganites

Effect of Mn doping on magnetic and transport properties of Nd0.5Sr0.5Co(1−y)MnyO3

Investigation of magnetic, electronic- and magneto-transport properties of Nd0.5Sr0.5Co(1−y)MnyO3 has been carried out with y=0–1. These studies, in effect, simultaneously reveal the effect of Mn doping on a ferromagnetic-metallic system Nd0.5Sr0.5CoO3 as well as the effect of Co doping on the antiferromagnetic-insulating system Nd0.5Sr0.5MnO3. Our linear/nonlinear ac susceptibility and dc magnetization measurements indicate that in both the cases ferromagnetic–paramagnetic transition temperature decreases and resistivity increases. The magnetoresistance of the samples in the lowest temperature which is nearly zero for Nd0.5Sr0.5CoO3, has been found to increase monotonically with the increase of Mn substitution. This effect is attributed to the phase separation scenario. Upon increasing the concentration of Co in Nd0.5Sr0.5MnO3 no indication of ferromagnetic–metallic phase is observed.

Alternating-Current Transport Properties in Nd0.7Sr0.3MnO3 Ceramic with Secondary Phases

Nd0.7Sr0.3MnO3 ceramics with secondary phases were prepared by ball-milling and post heat- treatment at 1623 K for 3, 7 and 13 h, respectively. The results from x-ray diffraction and energy dispersed spectroscopy show that some secondary phases are introduced and grow gradually with sintering time. These secondary phases have significant effects on the ac transport. For all the samples, the real part of impedance (Zr) decreases with increasing frequency and the Zr peak moves to a higher temperature. Interestingly, for a given frequency the Zr peak decreases with sintering time. However, for samples B and C which were sintered for a longer time than sample A, an additional Zr peak appears at a higher temperature and gradually increases with sintering time. The reposition of trapped charges in phase/grain boundaries or secondary phases is supposed to be responsible for the unusual relaxation process.

Density of states, magnetic and transport properties of Nd doped two dimensional perovskite compound Sr2CoO4

Structures, transport, magnetic properties, and first principle calculation results will be reported for the two dimensional layered structured perovskite compounds Sr2-xNdxCoO4 (x = 0.5, 0.75, 1, 1.25). Structure refinement results revealed that these compounds crystallized in K2NiF4-type structures with space group I4/mmm. The temperature dependence of resistivity showed semiconductor like behavior for these samples. It was found that the lattice parameter c decreases as the doping level x increases. The compounds exhibited a paramagnetic to ferromagnetic transition at temperatures of about 170, 125 K for the x = 1 and 0.75 samples, respectively. The temperature dependence of resistivity for the samples can be well fitted by the 2D variable hoping (VRH) model ρ = ρo exp(T0/T)1/3 (where ρo is a material specific characteristic conductance, with unit Ω−1, T0 is a material specific characteristic temperature in K) over the whole measured temperature range. First principles calculations indicated that the Nd doped Sr2CoO4 compounds show high spin polarization.

Control of magnetic and transport properties in Nd0.45Sr0.55MnO3 films through epitaxial strain

The influence of epitaxial strain, tuned with tetragonal distortion c/a from 0.965 to 1.034 by choosing different substrates and varying film thickness, on the magnetic and transport properties of Nd0.45Sr0.55MnO3 thin films has been investigated. It is found that epitaxial strain, depending on the value of c/a, can enhance or decrease the stability of A-type AF to induce ferromagnetic fluctuation and C-type AF instead of A-type AF.

Effect of cobalt substitution on magnetic and transport properties of Nd0·5Sr0·5Mn1−x Co x O3 (x = 0·1, 0·3 and 0·5)

The magnetic and transport properties of the compounds Nd0·5Sr0·5Mn\(_{{\rm 1}-{x}}\)Co\(_{{x}}\)O3 (x = 0·1, 0·3 and 0·5), synthesized by citrate–gel route have been investigated. The spin transition in cobaltates at low temperatures affects the magnetic as well as transport properties. The irreversibility behaviour between the zero-field cooled (ZFC) and field cooled (FC) magnetization as a function of temperature becomes stronger with increasing Co content. This is understood on the basis of glassy behaviour, which becomes more robust with increasing Co substitution. The non-saturating M–H behaviour indicates strong magnetic inhomogeneities which may cause the magnetic phase separation at the nanoscopic length scale. The double exchange interaction is stronger between Mn3 + –O2 − –Mn4 + as compared to Co3 + –O2 − –Co4 + pairs. Co-substitution suppresses the double exchange which will lead to cluster/spin glass like behaviour as well as semiconducting features due to localization of charge carriers (mobile \({e}_{\rm g}\) electrons).

Influence of Cr-doping on the magnetic and electrical transport properties of Nd 0.75Na 0.25MnO 3

Polycrystalline Nd 0.75Na 0.25Mn 1- x Cr x O 3 (0= x=0.1) samples were prepared by sol-gel method and their magnetic and electrical transport properties were investigated experimentally. The parent compound with x=0 was a charge ordered manganite and the charge ordering transition occurred at 170 K. For lower Cr concentration ( x<0.03), the samples preserved the charge ordering features of the parent compound, but the charge ordering transition temperature decreased with increasing x, in particular from 170 K for x=0 to 154 K for x=0.02. For the x≥0.03 samples, paramagnetic to ferromagnetic phase transition took place and the Curie temperature increased from 112.8 K for x=0.04 to 125.5 K for x=0.1. The electrical transport properties were also influenced by Cr doping. For x<0.03, the samples displayed insulator characteristics below 300 K. For x=0.04, the sample showed insulator-metal transition around 75 K. For x≥0.05, the insulator-metal transition disappeared and the compounds showed insulator features again. The magnetic and electrical properties could be well explained by the phase separation scenario.

Impact of magnetic phase coexistence on magnetotransport in polycrystalline Nd0.51Sr0.49MnO3 thin film

We report the magnetic and transport properties of Nd0.51Sr0.49MnO3 polycrystalline thin films (thickness ∼ 100 nm) prepared by dc magnetron sputtering on single crystal Y-stabilized ZrO2(1 0 0) substrates. The paramagnetic (PM) to ferromagnetic (FM) transition at TC = 260 K is followed by A-type antiferromagnetic (AFM) ordering at and charge ordered (CO) phase having the CE type spin order at . The strong CO-AFM transition observed at TCO ∼ 150 K at half doping is softened by a small increase in the Nd concentration and the disorder due to the polycrystalline nature of these films. The multiple magnetic transitions are suggestive of strong phase coexistence. In this study the insulator-like to metal-like transition temperature TIM ∼ 140 K is considerably lower than the TC and remains independent of the external magnetic field up to 70 kOe. This suggests that electrical transport is dominated by grain boundaries and has percolation type characteristics due to the existence of metallic (FM + A-AFM) and insulating (CO-AFM + GB) paths. The films show large magnetoresistance at low as well as high magnetic fields.

Magnetic cluster glass behavior and grain boundary effect in Nd0.7Ba0.3MnO3 nanoparticles

The magnetic and transport properties of Nd0.7Ba0.3MnO3 nanoparticles were explored by transmission electron microscopy, x-ray powder diffraction, resistivity, magnetoresistance, thermopower (S), and magnetic measurements. The metal-insulator transition behavior of the temperature dependence of resistivity for the sample with the largest particle size changes to insulating nature with the decrease in the particle size due to the enhancement of the grain boundary effect. The magnetoresistance of the nanoparticles is analyzed in the light of a phenomenological model based on the spin polarized tunneling at the grain boundaries. The thermopower of the samples shows a crossover from negative to positive values and at high temperatures S follows adiabatic small polaron hopping theory. The zero field cooled and field cooled (FC) magnetizations display broad ferromagnetic transition. The Curie temperature (TC) and the irreversibility temperature (Tirr) decrease considerably with the decrease in the particle size. During cooling the ac susceptibility of the nanoparticles exhibits two magnetic phase transitions with paramagnetic, ferromagnetic, and glassy phases. The frequency dependent peak in the out of phase part (χ″) of the ac susceptibility is the signature of cluster glass behavior. Large thermomagnetic irreversibility, monotonic increase in the FC magnetization, nonsaturation of the magnetization, and the observation of two distinct magnetic transitions in ac susceptibility give evidence for the cluster glass nature of the nanoparticles.

Structural and transport properties of Nd doped (Bi,Pb)-2212

We report here the effect of Nd substitution (at Sr site) on the crystallographic, normal, and superconducting state properties of the high temperature superconductor Bi 1.7Pb 0.4Sr 2− x Nd x Ca 1.1Cu 2.1O y (0.0 ⩽ x ⩽ 0.5). The structural and compositional analysis [X-ray diffraction analysis (XRD) and energy dispersive X-ray analysis (EDX), respectively] reveals that Nd ions enter into the Sr site of (Bi,Pb)-2212 crystal structure and scanning electron microscopy (SEM) results show a morphological change for higher concentration of Nd. The low temperature thermal and electrical transport measurements, electrical resistivity ( ρ), thermoelectric power (TEP) and thermal conductivity ( κ) show significant variations in critical temperature ( T C) as well as normal state properties upon Nd substitution. The sign reversal and the palpable variation in the magnitude of TEP as a function of Nd composition shows that Nd substitution at Sr site decreases the hole concentration. As the Nd concentration increases, the magnitude of ρ increases whereas κ decreases, which is in good agreement with the reduced electronic contribution towards the total thermal conductivity. The critical current density is found to be much higher for the optimum level of Nd substitution than those of pristine sample. These changes in the thermal and electrical transport properties are attributed to the decrease in the hole concentration in the Cu–O planes, which changes the system from ‘over-doped’ to ‘optimal-doped’ and then to ‘under-doped’ condition.

Ultrasonic Study on Charge Ordering in Nd0:5Ca0:5Mn1xAlxO3 (x=0,0.03)

The ultrasonic, magnetic and transport properties of Nd0:5Ca0:5Mn1xAlxO3 (x=0,0.03) were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0:5Ca0:5MnO3 undergoes a charge ordering transition at TCO 257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below TCO accompanied by an attenuation peak were observed. These features imply a strong electron-phonon interaction via the Jahn-Teller effect in the sample. Another broad attenuation peak was observed at around Tp 80 K. This anomaly is attributed to the phase separation between the antiferromagnetic (AFM) and paramagnetic (PM) phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0:5Ca0:5MnO3 are both partially suppressed by replacing Mn with Al.

Reentering spin glass behavior and charge ordering in phase separation Nd0.5Ca0.5MnO3 system

Half-doped manganese oxides are very important on clarifying physical mechanism of strong correlation electron system and colossal magnetoresistance (CMR) effec t due to their rich physical content. The structure, electrical and magnetic tra nsport properties of Nd0.5Ca0.5MnO3 manganite w as systemically studied. The results show that Nd0.5Ca0.5 MnO3 compound displays the O′-orthorhombic structure and indicate th e existence of the typical Jahn-Teller distortion under 300 K. The transport pro perties show that the system undergoes paramagnetic insulator-ferromagnetic meta l transition under a magnetic field of 8 T and is accompanied by CMR effect. Mea nwhile, it is found that the temperature of antiferromagnetic transition and cha rge ordering is around 150 and 240K, respectively. There appears a typical reent rant spin glass behavior around 41K and the negative magnetization is also obser ved in the compound. All these phenomena indicate that there exist several comp lex magnetic interactions in the ground state of this half-doped Nd0.5Ca0.5MnO3 compound at low temperature. The present result s provide experimental data for strongly electronic correlated system of manga nites.

Magnetic and transport properties of Nd 1.67Sr 0.33NiO 4

Nd 1.67Sr 0.33NiO 4 polycrystals have been prepared by modified sol–gel method and subsequent annealing. X-ray diffraction analysis, electrical resistivity, magnetic susceptibility and thermal magnetisation have been measured. Rietveld analyses show a tetragonal or pseudo-tetragonal K 2NiF 4-type structure. The resistivity measurements present a change in conduction mode close to 230 K, which corresponds to the charge ordering temperature. Below this temperature, the material adopts a variable range hopping conduction mode; and above, the conduction follows adiabatic thermal activated mode. The magnetic measurements show paramagnetic behaviour in the range of 80–300 K. Moreover, the magnetic susceptibility data show a sign of the charge ordering transition about 230 K.

Charge ordering, magnetic, electrical transport and thermal transport properties of Nd 0.75Na 0.25MnO 3 manganite

The electron diffraction patterns of Nd 0.75Na 0.25MnO 3 were recorded at various temperatures. Superlattice reflection spots were observed below 170 K, which provides direct evidence of an ordered arrangement of Mn 3+ and Mn 4+ cations in this compound at low temperature. By further analyzing the diffraction patterns, the Mn 3+ and Mn 4+ ions were found to form zigzag chains in the a– c plane of the orthorhombic lattice (space group Pnma). The magnetic, electrical-transport and thermal-transport properties of the compound were also studied. It is found that the specimen shows insulator-like characteristics in zero field, whereas a re-entrant ferromagnetic metal transition is observed when a strong magnetic field is applied. The ratio of the thermal conductivity to the electrical conductivity strongly deviates from the Wiedemann–Franz law , even in the ferromagnetic metallic state.

Effect of Pr Doping on Transport Properties of Nd(Ba2-xPrx)Cu3O7+δ

Solid-state-reacted polycrystalline Nd(Ba2-xPrx)Cu3O7+δ materials have been prepared and investigated using X-ray diffraction and resistivity measurements. Our results show that Nd(Ba2-xPrx)Cu3O7+δ is a superconductor when x<0.3. The Tc depression in superconductivity of Pr at Ba sites is due to both hole filling/localization and depairing effects. The normal state conductivity undergoes a dimensional crossover from two-dimensional to three-dimensional in the frame of the variable range hopping regime. The localization length of carriers shows that Pr doping localizes carriers in the normal state and causes the Tc depression. The magnetoresistance of the samples has been investigated within the thermally activated flux creep (TAFC) and Ambegaokar and Halperin (AH) phase slip models. The pinning energy and critical current density decrease with the applied magnetic field and Pr doping. A scaling relation as a power-law dependence of pinning energy on the magnetic field has been obtained. The derived pinning energy shows that Pr doping plays the role of a weak link.

Effect of nonstoichiometric disorder on the transport properties of Nd 2− xCe xCuO 4+ δ single crystal films

The effect of doping and nonstoichiometric disordering on the anisotropy of resistivity of Nd 2− x Ce x CuO 4+ δ single crystal films ( x=0.12; 0.15; 0.17) with (0 0 1) and (11̄0) orientations was investigated. We have found that the increase in the nonstoichiometric disorder leads to the growth of resistivity and to the change in the temperature dependence of the in-plane resistivity from ρ ab ( T)∼ T 2 to ρ ab ( T)∼exp( T/ T 0) −1/2. For most stoichiometric reduced films the conduction mechanism appears to be different between ab- and c-directions: a combination of in-plane metallic (d ρ ab /d T>0) and out-of-plane nonmetallic (d ρ c /d T<0) behavior is a real evidence of the 2D-character of the system investigated. The crossover from 2D to 3D was demonstrated to take place with increasing nonstoichiometric disorder.

Effect of crystallinity on the transport properties of Nd0.67Sr0.33MnO3 thin films

Highly crystalline Nd0.67Sr0.33MnO3 (NSMO) thin films were grown on (001) LaAlO3 (LAO) substrates using pulsed-laser deposition. By studying the microstructural properties of NSMO using x-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM, we have found that high degree crystallinity leads to improved transport properties such as smaller resistivities at both peak and room temperatures. A peak temperature of 187 K has been observed from a resistivity-temperature measurement, and around 200 K from a magnetization measurement.

Relations between structural distortions and transportproperties in Nd0.5Ca0.5MnO3 strained thinfilms

Strained thin films of charge/orbital-ordered (CO/OO) Nd0.5Ca0.5MnO3 with various thicknesses havebeen grown on (100) SrTiO3 and (100) LaAlO3 substrates, byusing the pulsed laser deposition technique. The thicknessof the films drastically influences the transport properties. Asthe thickness decreases, the CO transition becomes more favouredwhile at the same time the insulator-to-metal transition temperaturebecomes less favoured under application of a 7 T magnetic field. Clearrelationships between the structural distortions and thetransport properties are established. They are explained on thebasis of the elongation and the compression of the Mn-O-Mn andMn-O bond angles and distances of the Pnma structure,which modify the bandwidth and the Jahn-Teller distortion inthese materials.

Synthesis, characterization, magnetism and transport properties of Nd 1− xSr xCoO 3 perovskites

We have prepared polycrystalline, single-phase Nd 1− x Sr x CoO 3 materials (0≤ x≤0.40) using the nitrate decomposition method and we have studied how their structural, magnetic and transport properties change upon Sr 2+ doping. In this context we find that these series of compounds crystallize in GdFeO 3-type perovskite structures whose cell volume increases as x gets higher. From the magnetic point of view, this doping makes the materials evolve towards a ferromagnetic behavior as x increases, so that for x>0.20 the samples are already ferromagnetic below a T c∼225 K. Also, their electrical conductivity progressively increases with x. Nevertheless the materials remain semiconducting for x≤0.30 and only the sample with x=0.40 displays a M–I transition as a function of temperature ( T MI∼160 K).