Grain-Size Effects and the Physical Properties of La0.7Ca0.3MnO3-δ

2005 ◽  
Vol 277-279 ◽  
pp. 929-934 ◽  
Author(s):  
H.K. Lee ◽  
Horst Baier ◽  
J.S. Park ◽  
Y.P. Lee ◽  
Youn Seoung Lee
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Physical Properties ◽  
Size Effects ◽  
Annealing Temperature ◽  
Oxygen Deficiency ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Grain Sizes

The effects of grain-size in La0.7Ca0.3MnO3-δ (LCMO) system have been studied in connection with the magnetic and electronic properties. LCMO system prepared by the solid-state reaction was annealed in air at 1200, 1300 and 1400°C. The grain sizes of LCMO samples become larger with increasing of annealing temperature (TA ). The magnetization in LCMO samples increased while the coercive field decreased with increasing TA. The conductivity increased and the metal-insulator transition temperature TM-I decreased with increasing of TA. These physical properties are due to the oxygen deficiency caused by the increase of grain size. Finally, it was found that the grain size and the mechanical connection between grains play an important role in determining the electronic and magnetic properties.

Effects of different sintering temperatures on microstructural, transport, and magnetic properties of La0.93Sb0.07MnO3 compound

2014 ◽  
Vol 28 (24) ◽  
pp. 1450166
Author(s):  
Q. Wang ◽  
P. Duan ◽  
J. Y. Wang ◽  
L. Chang ◽  
J. X. Deng ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Solid State ◽  
Lattice Distortion ◽  
Solid State Reaction Method ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Reaction Method ◽  
Different Temperatures

Polycrystalline La 0.93 Sb 0.07 MnO 3 ceramics were synthesized using solid-state reaction method. The samples were sintered at different temperatures ranging from 1100°C to 1200°C. It is observed that microstructural, transport and magnetic properties of La 0.93 Sb 0.07 MnO 3 compounds strongly depend on sintering temperatures (TS). With TS increasing, the degree of lattice distortion has been weakened, the grain size has become larger and grain boundaries have decreased. Furthermore, the resistivity was reduced, and metal–insulator transition temperature was enhanced; the saturation magnetization per unit mass has decreased with TS increasing. These effects of different TS on physical properties can be explained by the structure distortion and grain boundary contributions for La 0.93 Sb 0.07 MnO 3 compounds.

Magnetic, Electronic - and Magneto - Transport Properties of Nanocrystalline Nd0.6Sr0.4MnO3 Manganites

2009 ◽  
Vol 67 ◽  
pp. 131-136 ◽  
Author(s):  
Kundu Sourav ◽  
Kumar Nath Tapan
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Transition Temperature ◽  
Curie Temperature ◽  
Transport Properties ◽  
Significant Variation ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Low Field

We have reported in this paper, the effect of grain size in Nd0.6Sr0.4MnO3 .We have investigated the effect of grain size on metal-insulator transition and Curie temperature. We have also reported here the variation of low field magnetoresistance with temperature and grain size. We have observed that the Curie temperature increases monotonically with particle size. The metal insulator transition temperature initially increases with particle size and then gets fixed to a certain value. In these Nd0.6Sr0.4MnO3 nanometric systems, any significant variation of magnetoresistance with particle size is not observed.

TRANSPORT PROPERTIES OF Ag-DOPED La0.7Ca0.3MnO3 THIN FILMS ON SILICON SUBSTRATE

2010 ◽  
Vol 24 (27) ◽  
pp. 5451-5456 ◽  
Author(s):  
H. C. JIANG ◽  
W. L. ZHANG ◽  
X. F. CAO ◽  
W. X. ZHANG ◽  
B. PENG
Keyword(s):  
Thin Films ◽  
Transition Temperature ◽  
Transport Properties ◽  
Silicon Substrate ◽  
Annealing Temperature ◽  
Rf Magnetron Sputtering ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Higher Temperature

Ag -doped La 0.7 Ca 0.3 MnO 3 (LCMO) films were prepared on silicon substrate by RF magnetron sputtering. The dependences of transport properties on annealing temperature were explored. It is shown that the resistivity of the samples decreases and the metal–insulator transition temperature shifts to higher temperature with the increase in annealing temperature. Two metal–insulator transition temperatures are presented in the R – T plots of Ag -doped LCMO films, which can be explained by the Ag 1+ substitution of La 3+ to form La 1-x Ag x MnO 3 compound. Compared with LCMO thin films, Ag -doping can observably improve the TM-I and decrease the resistivity of the samples.

A Novel Type of Magnetic Fe2O3/Fe3O4 Heterogeneous Microparticles Prepared via the Ethanol-Water Reflux and Rapid Combustion Process

2020 ◽  
Vol 20 (5) ◽  
pp. 2998-3003
Author(s):  
Jia Liu ◽  
Zhou Wang ◽  
Yanyan Wang
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Calcination Temperature ◽  
Ethyl Alcohol ◽  
Combustion Process ◽  
Key Factors ◽  
Absolute Ethyl Alcohol ◽  
Grain Sizes ◽  
Rapid Combustion

A novel type of magnetic Fe2O3/Fe3O4 heterogeneous microparticles with ellipsoidal macropores was prepared via the ethanol-water reflux and rapid combustion process. The experimental results showed that the volume of absolute ethyl alcohol and the calcination temperature were the key factors to the grain sizes and the magnetic properties, the calcination temperature largely affected the saturation magnetization and the grain size of Fe2O3/Fe3O4 heterogeneous microparticles, and the amount of absolute ethyl alcohol also tremendously affected the saturation magnetization, however, the amount of absolute ethyl alcohol affected little on the grain size. Fe2O3/Fe3O4 heterogeneous microparticles calcined at 200 °C for 1 h with absolute ethyl alcohol of 20 mL had the largest saturation magnetization of 90.1 Am2/kg.

scholarly journals Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 Ceramics

2019 ◽  
pp. 33-44 ◽  
Keyword(s):  
Transition Temperature ◽  
Frequency Dispersion ◽  
Insulator Transition ◽  
X Ray Diffraction ◽  
Phonon Modes ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Solid State Route ◽  
Distorted Structure ◽  
Lower Temperature

The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.

scholarly journals The Influence of Annealing Temperature on the Structure and Magnetic Properties of Nanocrystalline BiFeO3 Prepared by Sol–Gel Method

2021 ◽  
Author(s):  
T. Pikula ◽  
T. Szumiata ◽  
K. Siedliska ◽  
V. I. Mitsiuk ◽  
R. Panek ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Weak Ferromagnetism ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Average Grain Size ◽  
Spin Cycloid

AbstractIn this work, BiFeO3 powders were synthesized by a sol–gel method. The influence of annealing temperature on the structure and magnetic properties of the samples has been discussed. X-ray diffraction studies showed that the purest phase was formed in the temperature range of 400 °C to 550 °C and the samples annealed at a temperature below 550 °C were of nanocrystalline character. Mössbauer spectroscopy and magnetization measurements were used as complementary methods to investigate the magnetic state of the samples. In particular, the appearance of weak ferromagnetic properties, significant growth of magnetization, and spin-glass-like behavior were observed along with the drop of average grain size. Mössbauer spectra were fitted by the model assuming cycloidal modulation of spins arrangement and properties of the spin cycloid were determined and analyzed. Most importantly, it was proved that the spin cycloid does not disappear even in the case of the samples with a particle size well below the cycloid modulation period λ = 62 nm. Furthermore, the cycloid becomes more anharmonic as the grain size decreases. The possible origination of weak ferromagnetism of the nanocrystalline samples has also been discussed.

Contribution to the study of the metal-insulator transition in the system II. Magnetic properties

1972 ◽  
Vol 11 (1) ◽  
pp. vii
Author(s):  
J.P. Pouget ◽  
P. Lederer ◽  
D.S. Schreiber ◽  
H. Launois ◽  
D. Wohlleben ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

Orbital change manipulation metal–insulator transition temperature in W-doped VO2

2015 ◽  
Vol 17 (17) ◽  
pp. 11638-11646 ◽  
Author(s):  
Xinfeng He ◽  
Yijie Zeng ◽  
Xiaofeng Xu ◽  
Congcong Gu ◽  
Fei Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Infrared Spectroscopy ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
First Principles ◽  
Insulator Transition ◽  
First Principles Calculations ◽  
Orbital Structure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Using ultraviolet-infrared spectroscopy and first principles calculations, it is revealed that changes in the orbital structure can regulate the W-doped VO2 phase transition temperature.

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