scholarly journals Magnetic and Transport Studies of Strongly Correlated Perovskite Ceramics

2021 ◽  
Author(s):  
◽  
Erwan Hemery
Keyword(s):  
Transition Temperature ◽  
Thermoelectric Power ◽  
Transition Metal Oxides ◽  
Magnetic Measurements ◽  
Oxygen Deficiency ◽  
Double Perovskite ◽  
Charge Ordering ◽  
Power Measurement ◽  
Ferromagnetic Transition ◽  
Strongly Correlated

<p>This thesis describes the results from an experimental study of the magnetic and transport properties of two strongly correlated transition metal oxides. The firstmaterial under study is the ferromagnetic half-metal double perovskite, Sr2FeMoO6, in which we have made isoelectronic (Ba2+) and electronic (La3+) substitutions onto the strontium site. Magnetoresistance measurements on Sr2-xBaxFeMoO6 revealed that the low temperature magnetoresistance is dominated by inter-grain transport while the intra-grain contribution is evident when the temperature is close to the ferromagnetic transition temperature. Transport measurements on Sr2-xLaxFeMoO6 clearly showed that the doping dependence of the thermoelectric power is surprisingly similar to the one observed in the superconducting cuprates. In addition, it was found that the electronic doping leads to an increase in the ferromagnetic transition temperature, which supports the band filling model. Substitution on the Fe site was also investigated by partially replacing Fe with the non-magnetic aluminium element (Sr2Fe1-xAlxMoO6). It was found from thermoelectric power measurement that the Fe electronic state is below3+,which is inconsistentwith theoretical models but is in good agreement with Mossbauer measurements. In addition, magnetic measurements showed that the reduction in the ferromagnetic ordering temperature could be explained in terms of a 3D percolation model. The second compound is the oxygen deficient strontium iron oxide SrFeO3-delta . The temperature dependence of the thermoelectric power was measured in this compound for the first time and shown to be reminiscent of the charge-ordering Verwey transition observed in Fe3O4. Magnetic measurements show an increase of a weak ferromagnetic signal versus the oxygen deficiency that could originate from a Dzyaloshinsky-Moriya interaction in the distorted FeO6 octahedra. Finally, we observed a large magnetoresistance near room temperature for compounds close to the orthorhombic SrFeO2.75 phase.</p>

scholarly journals Magnetic and Transport Studies of Strongly Correlated Perovskite Ceramics

2021 ◽  
Author(s):  
◽  
Erwan Hemery
Keyword(s):  
Transition Temperature ◽  
Thermoelectric Power ◽  
Transition Metal Oxides ◽  
Magnetic Measurements ◽  
Oxygen Deficiency ◽  
Double Perovskite ◽  
Charge Ordering ◽  
Power Measurement ◽  
Ferromagnetic Transition ◽  
Strongly Correlated

<p>This thesis describes the results from an experimental study of the magnetic and transport properties of two strongly correlated transition metal oxides. The firstmaterial under study is the ferromagnetic half-metal double perovskite, Sr2FeMoO6, in which we have made isoelectronic (Ba2+) and electronic (La3+) substitutions onto the strontium site. Magnetoresistance measurements on Sr2-xBaxFeMoO6 revealed that the low temperature magnetoresistance is dominated by inter-grain transport while the intra-grain contribution is evident when the temperature is close to the ferromagnetic transition temperature. Transport measurements on Sr2-xLaxFeMoO6 clearly showed that the doping dependence of the thermoelectric power is surprisingly similar to the one observed in the superconducting cuprates. In addition, it was found that the electronic doping leads to an increase in the ferromagnetic transition temperature, which supports the band filling model. Substitution on the Fe site was also investigated by partially replacing Fe with the non-magnetic aluminium element (Sr2Fe1-xAlxMoO6). It was found from thermoelectric power measurement that the Fe electronic state is below3+,which is inconsistentwith theoretical models but is in good agreement with Mossbauer measurements. In addition, magnetic measurements showed that the reduction in the ferromagnetic ordering temperature could be explained in terms of a 3D percolation model. The second compound is the oxygen deficient strontium iron oxide SrFeO3-delta . The temperature dependence of the thermoelectric power was measured in this compound for the first time and shown to be reminiscent of the charge-ordering Verwey transition observed in Fe3O4. Magnetic measurements show an increase of a weak ferromagnetic signal versus the oxygen deficiency that could originate from a Dzyaloshinsky-Moriya interaction in the distorted FeO6 octahedra. Finally, we observed a large magnetoresistance near room temperature for compounds close to the orthorhombic SrFeO2.75 phase.</p>

Oxygen Isotope Effect in Ordered PrBaMn2O6

2012 ◽  
Vol 190 ◽  
pp. 699-702 ◽  
Author(s):  
A.N. Taldenkov ◽  
N.A. Babushkina ◽  
A.V. Inyushkin ◽  
V.S. Kalitka ◽  
A.R. Kaul
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Oxygen Isotope ◽  
Isotope Effect ◽  
Charge Ordering ◽  
Ferromagnetic Transition ◽  
Small Decrease ◽  
Ac Magnetic Susceptibility ◽  
Isotope Substitution ◽  
Systematic Shift

The oxygen isotope effect in ordered half-doped manganite PrBaMn216-18O6 has been investigated. Real and imaginary parts of ac magnetic susceptibility, dc magnetization and magnetoresistance were measured at temperatures from 4.2 to 320 K in applied magnetic field up to 35 kOe. Substantial increase of charge ordering (CO) transition temperature TCO under oxygen isotope substitution 16O 18O and small decrease of ferromagnetic (FM) transition temperature TFM were found. Small systematic shift of ferromagnetic transition temperature in oxygen reduced manganite PrBaMn216 18O5 is also considered. The obtained results are compared with those observed in other manganites demonstrating the large isotope effect.

Oxygen Isotope Effect in Cr- and Ru-Doped Pr0.5Ca0.5MnO3 Manganites

2009 ◽  
Vol 152-153 ◽  
pp. 127-130 ◽  
Author(s):  
N.A. Babushkina ◽  
A.N. Taldenkov ◽  
A.V. Inyushkin ◽  
Antoine Maignan ◽  
D.I. Khomskii ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Metallic Phase ◽  
Charge Ordering ◽  
Ferromagnetic Phase ◽  
Ferromagnetic Transition ◽  
Isotope Substitution ◽  
The Difference ◽  
A Charge ◽  
Ordering Transition ◽  
Ordered State

The effect of 16О → 18О isotope substitution on the properties of Pr0.5Ca0.5MnO3 manganites doped by Cr and Ru is studied. In these compounds, chromium and ruthenium favor (i) the suppression of a charge-ordered state and (ii) the formation of a ferromagnetic metallic phase. The 16О → 18О isotope substitution leads to the growth of the charge-ordering transition temperature (TCO), and to the lowering of ferromagnetic transition temperature (TFM) accompanied by a decrease in the content of ferromagnetic phase. The difference in the behavior of the Cr- and Ru-substituted samples is analyzed.

Conduction Characteristics of Charge Ordering Type Ferroelectrics,YFe2O4

2006 ◽  
Vol 966 ◽  
Author(s):  
Ken Imamura ◽  
Yoichi Horibe ◽  
Takeshi Yoshimura ◽  
Norifumi Fujimura ◽  
Shigeo Mori ◽  
...  
Keyword(s):  
Room Temperature ◽  
Inflection Point ◽  
Oxygen Deficiency ◽  
Complex Impedance ◽  
Charge Ordering ◽  
Neel Temperature ◽  
Ohmic Conduction ◽  
Néel Temperature ◽  
Impedance Measurements ◽  
Conduction Properties

ABSTRACTElectrical conduction properties of charge ordering type ferroelectrics YFe2O4 were investigated. YFe2O4 was synthesized in reduced atmosphere at 1200 °C. Oxygen partial pressure of the reduced atmosphere was controlled by the equilibrium state of CO and CO2. YFe2O4 is paramagnetic at room temperature and has Néel temperature around 250K. The Néel temperature was decreased with increasing the amount of oxygen deficiency. Moreover, YFe2O4 showed ohmic conduction from 260 to 100 K. The temperature dependence of the DC conductivity showed an inflection point at the Néel temperature, which indicated the development of charge ordering of Fe2+ and Fe3+ ions. From the complex impedance measurements, the equivalent circuits of YFe2O4 with different oxygen deficiency were determined at various temperatures.

Superconductivity of embedded lead nano particles in metallic and amorphous matrices

2001 ◽  
Vol 703 ◽  
Author(s):  
K. Chattopadhyay ◽  
V. Bhattacharya ◽  
A. P. Tsai
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Magnetic Measurements ◽  
Microstructural Characterization ◽  
Rapid Solidification Processing ◽  
Nano Particles ◽  
Superconducting Transition ◽  
Solidification Processing ◽  
Embedded Particles

ABSTRACTNanodispersed lead in metallic and amorphous matrices was synthesized by rapid solidification processing. The optimum microstructure was tailored to avoid percolation of the particles. With these embedded particles it is possible to study quantitatively the effect of size on the superconducting transition temperature by carrying out quantitative microstructural characterization and magnetic measurements. Our results suggest the role of the matrices in enhancement or depression of superconducting transition temperature of lead. The origin of this difference in behavior with respect to different matrices and sizes is discussed.

NOVEL MAGNETIC PROPERTIES IN MULTI-WALLED CARBON NANOTUBE MATS: CONSISTENT WITH THE PARAMAGNETIC MEISSNER EFFECT DUE TO ULTRAHIGH-TEMPERATURE SUPERCONDUCTIVITY

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4285-4296 ◽  
Author(s):  
GUO-MENG ZHAO ◽  
PIEDER BEELI
Keyword(s):  
Carbon Nanotube ◽  
Saturation Magnetization ◽  
Magnetic Measurements ◽  
Meissner Effect ◽  
Magnetic Data ◽  
Ferromagnetic Transition ◽  
Measured Concentration ◽  
Paramagnetic Meissner Effect ◽  
Multi Walled Carbon Nanotube ◽  
Ultrahigh Temperature

We report magnetic measurements up to 1200 K on iron-contaminated multi-walled carbon nanotube mats with a Quantum Design vibrating sample magnetometer. Extensive magnetic data consistently show a ferrromagnetic transition at about 1000 K and a ferromagnetic-like transition at about 1275 K. The ferromagnetic transition at about 1000 K is associated with an Fe impurity phase and its saturation magnetization is in quantitative agreement with the Fe concentration measured by an inductively coupled plasma mass spectrometer. On the other hand, the saturation magnetization for the ferromagnetic-like phase (at 1275 K) is about four orders of magnitude larger than that expected from the measured concentration of Co or CoFe . We show that this ultrahigh-temperature ferromagnetic-like behavior cannot be explained by ferromagnetism of any Fe -carbon phases, carbon-based phases, or magnetic impurities, but is consistent with the paramagnetic Meissner effect (orbital ferromagnetism) due to the existence of π Josephson junctions in a granular superconductor.

scholarly journals Preparation of InSe Thin Films by Thermal Evaporation Method and Their Characterization: Structural, Optical, and Thermoelectrical Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Sarita Boolchandani ◽  
Subodh Srivastava ◽  
Y. K. Vijay
Keyword(s):  
Thin Films ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Temperature Variation ◽  
Thermal Evaporation ◽  
Low Cost ◽  
High Vacuum ◽  
Power Measurement ◽  
Thermal Evaporation Method ◽  
Evaporation Method

The indium selenium (InSe) bilayer thin films of various thickness ratios, InxSe(1-x) (x = 0.25, 0.50, 0.75), were deposited on a glass substrate keeping overall the same thickness of 2500 Ǻ using thermal evaporation method under high vacuum atmosphere. Electrical, optical, and structural properties of these bilayer thin films have been compared before and after thermal annealing at different temperatures. The structural and morphological characterization was done using XRD and SEM, respectively. The optical bandgap of these thin films has been calculated by Tauc’s relation that varies within the range of 1.99 to 2.05 eV. A simple low-cost thermoelectrical power measurement setup is designed which can measure the Seebeck coefficient “S” in the vacuum with temperature variation. The setup temperature variation is up to 70°C. This setup contains a Peltier device TEC1-12715 which is kept between two copper plates that act as a reference metal. Also, in the present work, the thermoelectric power of indium selenide (InSe) and aluminum selenide (AlSe) bilayer thin films prepared and annealed in the same way is calculated. The thermoelectric power has been measured by estimating the Seebeck coefficient for InSe and AlSe bilayer thin films. It was observed that the Seebeck coefficient is negative for InSe and AlSe thin films.

Structure, Electrical and Magnetic Properties of Thin Films of La1−xMxMnO3 on Si

1999 ◽  
Vol 562 ◽  
Author(s):  
N. N. Mateeva ◽  
P. C. Hogan ◽  
K. H. Dahmen
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Buffer Layers ◽  
Ferromagnetic Transition ◽  
Electrical And Magnetic Properties ◽  
Insulator Metal Transition ◽  
Composition Structure

ABSTRACTThin films of lanthanum manganates doped with Ca2+, Sr2+, Ba2+ and Pb2+ have been deposited on Si(100) substrate and their electrical and magnetic properties were discussed with respect to the composition, structure and nature of the dopant. Buffer layers of YSZ and La0.8Al0.2O3 were employed and their effect on the materials was studied. Interesting magnetotransport properties were found in some of the films, where there is a large difference between the insulator-metal transition temperature and a ferromagnetic transition temperature.

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