scholarly journals Electrical transport and magnetoresistance of double layered CMR manganites R1.2Sr1.8Mn2O7(R = La, Pr, Sm)

2017 ◽  
Vol 35 (2) ◽  
pp. 440-446 ◽  
Author(s):  
Y.S. Reddy
Keyword(s):  
Electrical Resistivity ◽  
Electrical Transport ◽  
Sol Gel ◽  
Variable Range Hopping ◽  
Temperature Dependent ◽  
Lanthanide Ion ◽  
Colossal Magnetoresistive ◽  
Temperature Range ◽  
Three Samples ◽  
Temperature Dependent Resistivity

Abstract Polycrystalline bulk samples of double layered (DL) colossal magnetoresistive (CMR) manganites R1.2Sr1.8Mn2O7 (R = La, Pr, Sm) were prepared by sol-gel method to study the effect of size of lanthanide ion on their magnetotransport properties. The electrical resistivity of the samples was investigated in the temperature range of 70 K to 300 K at different magnetic fields. The samples LSMO and PSMO show insulator-to-metal transition (IMT) behavior, while SSMO sample exhibits insulating behavior in the entire temperature range with a very large value of resistivity. The insulator-to-metal transition temperature (TIM) decreases from 123 K (LSMO) to 90 K (PSMO) and disappears in SSMO sample. To explain the electrical transport above TIM, the temperature dependent resistivity data (T > TIM) of all the samples were fitted to the equations of different conduction models. The results indicate that the conduction at T > TIM is due to Mott variable range hopping (VRH) mechanism in the LSMO and PSMO samples, while Efros-Shkloskii (ES) type of VRH model dominates the conduction process in the SSMO sample. All the three samples show increasing magnetoresistance (MR) even below TIM and the maximum MR is shown by LSMO (39 % at 75 K, 3 T).

EFFECT OF Ba SUBSTITUTION ON ELECTRICAL TRANSPORT AND MAGNETORESISTANCE OF La1.2Sr1.8Mn2O7

2009 ◽  
Vol 23 (03) ◽  
pp. 447-460 ◽  
Author(s):  
Y. S. REDDY ◽  
P. KISTAIAH ◽  
C. VISHNUVARDHAN REDDY
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Electrical Transport ◽  
Sol Gel ◽  
Parent Compound ◽  
Temperature Dependent ◽  
Temperature Range ◽  
Anisotropic Lattice ◽  
Ba Substitution

Polycrystalline samples of double layered (DL) manganite system La 1.2( Sr 1-x Ba x)1.8 Mn 2 O 7(0.0≤×≤0.4) were prepared by the sol-gel method. The anisotropic lattice expansion is observed with the substitution of Ba 2+ into Sr 2+ sites. The electrical resistivity and magnetoresistance (MR) measurements were carried out over the temperature range 4.2 K–300 K. The substitution of Ba results in the suppression of T IM , insulator-to-metal transition temperature. A low temperature upturn of resistivity is seen in all the samples of the system, which is attributed to the spin-glass-like transition. The conduction mechanism above T IM is explained by Mott variable range hopping (VRH) mechanism. The variation of MR with temperature and applied magnetic field is discussed. From the temperature dependent MR curves, it is observed that the large MR values are present over a wide temperature range and the maximum MR values occur at [Formula: see text]. The x=0.4 sample exhibits ~31% of MR with the application of a mere 0.4 T field at 5 K, which accounts for ~35% enhancement of MR of parent compound (~23% of MR% at 0.4 T at 5 K). The MR — H data is fitted to the power law ρ = ρ0-αHn, and it is found that the low temperature MR varies as square root of the applied magnetic field, as expected in conventional metals.

High-Temperature Electrical Transport Property of Misfit Cobaltite of Ca3-xNdxCo4-xCuxO9 (x = 0.0 – 0.4)

2012 ◽  
Vol 584 ◽  
pp. 162-166 ◽  
Author(s):  
M. Senthilkumar ◽  
R. Vijayaraghavan
Keyword(s):  
Electrical Resistivity ◽  
Electrical Transport ◽  
Conduction Mechanism ◽  
Sol Gel ◽  
Combustion Method ◽  
Temperature Range ◽  
Conduction Behavior ◽  
Coupled Substitution ◽  
Xrd Patterns ◽  
Semiconducting Behavior

Polycrystalline samples of the Ca3-xNdxCo4-xCuxO9 (x = 0.0 - 0.4) were prepared by the sol-gel cum combustion method using sucrose to investigate the effects of the coupled substitution of Nd and Cu on Ca and Co sites simultaneously on electrical property of Ca3Co4O9 (Co349). The products were characterized by powder x-ray diffraction (XRD), thermogravimetry (TG) / differential thermal analysis (DTA) and scanning electron microscopy (SEM). Powder XRD patterns reveal the formation of single-phase products up to x = 0.4. Coupled substitution increases the solubility of Cu on Co site, in contrast to the limited solubility of Cu (x = 0.3) when separately substituted. TGA confirms the formation of the Ca3Co4O9 phase at around 680 0C. The grain size of the parent and substituted products is in the range of 200-250 nm. Electrical resistivity (ρ) measurement was performed in the temperature range of 300 - 800 K. Electrical resistivity (ρ) of parent sample shows metallic type conduction behavior up to 500 K and above 500 K, it shows semiconducting behavior. All the substituted compositions show semiconducting behavior with increasing electrical resistivity with increasing x. The conduction mechanism was also analyzed. Parent and substituted samples behave thermally activated conduction mechanism in the temperature range of 600 – 800 K.

Electrical Resistivity and Magnetoresistance of the δ-FeZn10 Complex Intermetallic Phase

2013 ◽  
Vol 1517 ◽  
Author(s):  
P. Koželj ◽  
S. Jazbec ◽  
J. Dolinšek
Keyword(s):  
Electrical Resistivity ◽  
Intermetallic Phase ◽  
Structural Complexity ◽  
Weak Localization ◽  
Intrinsic Disorder ◽  
Atomic Clusters ◽  
Charge Carriers ◽  
Temperature Dependent ◽  
Temperature Dependent Resistivity ◽  
Complex Metallic Alloys

ABSTRACTThe δ-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally-coordinated environments, fractionally occupied lattice sites and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. The electrical resistivity is large and exhibits a maximum at about 220 K. The magnetoresistance is sizeable, amounting to 1.5 % at 2 K in 9 T field. The temperature–dependent resistivity is discussed within the frame of the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating. A comparison to the theory of weak localization is also made.

Magnetic and electrical transport properties of Sr2Ti1−xCoxO4 ceramics by sol–gel

2017 ◽  
Vol 31 (17) ◽  
pp. 1750195
Author(s):  
Li Zhang ◽  
Yibao Li ◽  
Zhen Tang ◽  
Yan Deng ◽  
Hui Yuan ◽  
...  
Keyword(s):  
Transport Properties ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Sol Gel ◽  
Variable Range Hopping ◽  
Electrical Transport Properties ◽  
Co Doping ◽  
Hopping Model ◽  
Variable Range Hopping Model ◽  
Co Doped

Microstructures, electrical transport and magnetic properties of Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics are investigated. With Co doping, the Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics remain tetragonal structure while the grain size is decreased with doping. Magnetic moment is enhanced with Co doping and ferromagnetism is observed at low temperatures for Co-doped Sr[Formula: see text]TiO[Formula: see text]. The Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] and Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] show semiconductor-like transport properties, which can be well fitted by Mott variable range hopping model. The results will provide an effective route to synthesize Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics as well as to investigate the physical properties.

scholarly journals Existence of Partially Degenerate Electrical Transport in Intermetallic Cu2SnSe3 Thermoelectric System Sintered at Different Temperatures

2021 ◽  
Author(s):  
K. Gurukrishna ◽  
H. R. Nikhita ◽  
S. M. Mallikarjuna Swamy ◽  
Ashok Rao
Keyword(s):  
Electrical Resistivity ◽  
High Temperatures ◽  
Electrical Transport ◽  
Minority Carrier ◽  
Upward Movement ◽  
Temperature Dependent ◽  
Conventional Solid State Reaction ◽  
Different Temperatures ◽  
Transport Behaviour ◽  
Small Polarons

AbstractA detailed investigation on the temperature dependent electrical properties of Cu2SnSe3 system, synthesized via conventional solid-state reaction at different sintering temperatures are presented in this communication. All the samples exhibit degenerate semiconducting nature at low temperatures. The existence of small polarons and hence electron–phonon interactions are confirmed at temperatures below 400 K. A transition was observed from degenerate to non-degenerate semiconducting behaviour at high temperatures (T > 400 K). The study confirms the unusual transition in electrical resistivity as well as thermopower at high temperatures in all the compounds, demonstrating the existence of minority carrier excitation along with temperature-triggered ionisation of the defects. The transport behaviour is further supported by an upward movement of Fermi level away from the valence band. Highest weighted mobility of 8.2 cm2 V−1 s−1 at 673 K was obtained for the sample sintered at 1073 K. A considerable decrease in electrical resistivity with increase in temperature (T > 400 K) has driven the power factor to increase exponentially, thereby achieving highest value of 188 µV/mK2 (at 673 K) for the sample sintered at 673 K. Graphic abstract

scholarly journals Electrical Transport Properties ofNi95Ti5Catalyzed Multi wall Carbon Nanotubes Film

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Zishan Husain Khan ◽  
Numan Salah ◽  
Sami Habib
Keyword(s):  
Carbon Nanotubes ◽  
Temperature Region ◽  
Electrical Transport ◽  
Conduction Mechanism ◽  
Variable Range Hopping ◽  
Electrical Transport Properties ◽  
Multi Wall Carbon Nanotubes ◽  
Variable Range ◽  
Temperature Range ◽  
Dimensional Variable

Carbon nanotubes (CNTs) can be understood as one or more graphite sheets rolled up into a seamless cylinder. CNTs have gained much attention and scientific interest due to their unique properties and potential applications since their discovery in 1991. In the present work, we have deposited Ni95Ti5 film using thermal deposition method. Finally, theNi95Ti5catalyzed multi wall carbon nanotubes (MWNTs) are grown on silicon substrate using low pressure chemical vapor deposition (LPCVD) method and the electrical transport properties of this MWNTs film are studied over a temperature range (284–4K) to explain the conduction mechanism. We have suggested two types of conduction mechanism for the entire temperature range. For the temperature region (284–220K), the conduction is due to thermally activated process, whereas the conduction takes place via variable range hopping (VRH) for the temperature range of (220–4K). The VRH mechanism changes from three dimensions to two dimensions as we move down to the temperature below 50K. Therefore, the data for the temperature region (220–50K) is plotted for three dimensional variable range hopping (3D VRH) model and the two dimensional variable range hopping (2D VRH) for lower temperature range of (50–4K). These VRH models give a good fit to the experimental data. Using these models, we have calculated various interesting electrical parameters such as activation energy, density of states, hopping distance and hopping energy.

On the temperature dependent electrical resistivity of CNT layers in view of Variable Range Hopping models

2017 ◽  
Vol 43 ◽  
pp. 253-261 ◽  
Author(s):  
Kamil Kędzierski ◽  
Karol Rytel ◽  
Bolesław Barszcz ◽  
Anna Gronostaj ◽  
Łukasz Majchrzycki ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Variable Range Hopping ◽  
Temperature Dependent ◽  
Variable Range ◽  
Hopping Models

A SPECIAL ELECTRICAL TRANSPORT BEHAVIOR IN La0.67Sr0.33MnO3/CeO2 COMPOSITES

2008 ◽  
Vol 22 (25) ◽  
pp. 2517-2522
Author(s):  
GUANGMING REN ◽  
SONGLIU YUAN
Keyword(s):  
Experimental Data ◽  
Electrical Transport ◽  
Sol Gel ◽  
Simple Expression ◽  
Nominal Composition ◽  
Temperature Range ◽  
Transport Behavior ◽  
Insulator Metal Transition ◽  
Surface Magnetization ◽  
Straight Lines

The composites with the nominal composition of (1-x) La 0.67 Sr 0.33 MnO 3 (LSMO)/x CeO 2 were fabricated by the sol–gel method. A special electrical transport behavior is observed in the ρ/ρTp versus temperature curves, where ρTp is the peak resistivity at the insulator–metal transition temperature (Tp). The curves for all samples with different CeO 2 content are parallel in the high-T insulator regime and in a certain temperature range below Tp. Furthermore, a series of parallel straight lines can be found in the [Formula: see text] versus temperature curves for the samples with different CeO 2 content. By considering the surface magnetization at the grain boundary, we obtain a simple expression for the temperature dependence of resistivity that can reproduce the experimental data in the high-T insulator regime and in a certain temperature range below Tp.

Temperature dependent impedance spectroscopy and electrical transport mechanism in sol-gel derived MgCr2O4 spinel oxide

2020 ◽  
Vol 599 ◽  
pp. 412377
Author(s):  
Muhammad Javed ◽  
Ayaz Arif Khan ◽  
Muhammad Shafiq Ahmed ◽  
Said Nasir Khisro ◽  
Jamal Kazmi ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Electrical Transport ◽  
Transport Mechanism ◽  
Sol Gel ◽  
Spinel Oxide ◽  
Temperature Dependent

scholarly journals Essential role of enhanced surface electron–phonon interactions on the electrical transport of suspended polycrystalline gold nanofilms

RSC Advances ◽  
2018 ◽  
Vol 8 (37) ◽  
pp. 20679-20685 ◽  
Author(s):  
Tingting Miao ◽  
Dawei Li ◽  
Shaoyi Shi ◽  
Zhongli Ji ◽  
Weigang Ma ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Transport ◽  
Essential Role ◽  
Surface Electron ◽  
Phonon Interaction ◽  
Temperature Range ◽  
Electron Phonon Interaction ◽  
Polycrystalline Gold ◽  
Enhanced Surface

Considering the enhanced surface electron–phonon interaction, the electrical resistivity of suspended polycrystalline gold nanofilms with different length can be described very well in a temperature range from 2 K to 340 K.

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