Showing papers by "Pham Thanh Phong published in 2009"
TL;DR: In this paper, a thorough study for the critical behavior of La0.7A0.3 polycrystalline samples near ferromagnetic-paramagnetic phase transition temperature by analyzing isothermal magnetization data is presented.
51 citations
TL;DR: In this article, a phenomenological model based on spin-polarized transport of conduction electrons at the grain boundaries was proposed to explore the basic physics behind temperature dependence of low-field magnetoresistance.
35 citations
TL;DR: In this article, the authors report the resistivity (ρ) −temperature (T) patterns in (1 −x)La0,7Ca0,3MnO3+xAl2O3 composites (0≤x≤0.05) over a temperature regime of 50 −300 K.
34 citations
TL;DR: In this paper, the temperature dependence of the electrical resistivity in (1 − x ) La 0.7 Ca 0.3 MnO 3 ǫ+x Ag composites has been investigated between 5 and 300 k for H Â = 0 and 3 T, respectively, and the ρ-T of all samples fit well with the phenomenological percolation approach, which is based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions.
34 citations
TL;DR: In this paper, the effect of Al 2 O 3 on the low field magnetoresistance ( LFMR) of La 0.7 Ca 0.3 MnO 3 ǫ+ǫ x Al 2O 3 composite synthesized through a solid-state reaction method combined with an energy milling method was reported.
32 citations
TL;DR: In this article, the superparamagnetism of single-phase nanocrystalline particles was studied and the temperature dependence of the saturation magnetization showed a strong collective excitation due to the spin wave that depends on temperature.
23 citations
TL;DR: In this article, the depth of the resistance minima was found to increase with an increased Al 2 O 3 content, and the electron-electron (e-e) interaction and Kondo effects were found to be the dominant mechanism of low-temperature resistivity upturn of composites.
7 citations
01 Sep 2009
TL;DR: In this article, the spin polarized transport of conduction electrons at the grains boundaries was investigated and the experimental data (MR-H) agreed quite well with the dependence of temperature on tunneling magnetoresistance (TMR) described by an expression of Hwang et al.
Abstract: Magnetization and transport of (1 – x)La0.7Ca0.3MnO3 +xAg (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) composites has been reported in this paper. Low Field Magnetoresistance (LFMR), conductivity (σ) and metal – insulator transition temperature (Tp) increases with increasing content of Ag. Due to the presence of nomagnetic Ag in the ferromagnetic La0.7Ca0.3MnO3 material, dc magnetization decreases but the corresponding Tp increases. Based on the spin polarized transport of conduction electrons at the grains boundaries, we find that our experimental data (MR – H) agree quite well with the dependence of temperature on tunneling magnetoresistance (TMR) described by an expression of Hwang et al.
3 citations
01 Jan 2009
TL;DR: In this article, the effect of artificial grain boundaries on the electromagnetic properties of (1−x)La07Ca03MnO3 + xAl2O3 nanocomposites (x x= 0 x÷ 5wt%) was investigated based upon a spin-polarized tunneling mechanism.
Abstract: We have investigated the effect of artificial grain boundaries on the electromagnetic properties of (1–x)La07Ca03MnO3 + xAl2O3 nanocomposites (x x= 0 x÷ 5wt%) Based upon a spin-polarized tunneling mechanism we have proposed a phenomenological model to explain the observed electrical transport behavior over the whole temperature range (70 ÷ 300K), especially the gradual drop of metal-insulator transition temperature (Tp) as a function of increasing Al2O3 content, while the feromagnetic-paramagnetic transition temperature (TC) remains almost constant (TC x= 250K) A large low-field magneto-resistance was observed for all the composite samples and the largest magnetoresistance ratio was recorded for a composition with x x=001
1 citations