Giant magnetoresistance in fine particle of La0.67Ca0.33MnO3 synthesized at low temperatures

Chowdhury

Journal of Magnetism and Magnetic Materials

et al. 2002

The composites of La 2=3 Ca 1=3 MnO 3 :xSiO 2 (0pxp0:40) have been synthesized by sol-gel technique to derive homogeneous nanocomposites. Si 4þ by virtue of its strong preference for tetrahedral site does not enter the perovskite lattice. The percolation threshold composition has been determined by resistivity measurements at around 90% volume fraction of LCMO. A detailed electrical, magnetic and magneto-transport characterizations have been carried out for composites around the threshold composition (x ¼ 0:05; 0:10; 0:15). The magnetoresistance results at 1 T show a sharp peak at T c and a minimum just below T c as reported in several polycrystalline LCMO composites.

Section: Resultsmentioning

confidence: 99%

Solution sol–gel processing and investigation of percolation threshold in La2/3Ca1/3MnO3:xSiO2 nanocomposite

Chowdhury

Journal of Magnetism and Magnetic Materials

et al. 2002

Solid State Communications

“…For this class of materials, lower sintered temperatures (T s ) will be necessary as the grain size increases with T s . The effect of grain size on structural, magnetic and transport properties in hole-doped manganites has been extensively investigated [11][12][13][14][15][16][17]. All these researches indeed suggest that the magnetic properties are markedly affected by grain size.…”

mentioning

confidence: 99%

The effect of grain size on electrical transport and magnetic properties of La0.9Te0.1MnO3

Yang

Zhao

Zhang

et al. 2004

The effect of grain size on structural, magnetic and transport properties in were dissolved in diluted nitric acid in which an excess of citric acid and ethylene glycol was added to make a metal complex. After all the reactants had completely dissolved, the solution was mixed and heated on a hot plate resulting in the formation of a gel. The gel was dried at 250 °C, and then preheated to 600 °C to remove the remaining organic and to decompose the nitrates of the gel. The resulting powder was pressed into pellets, each of which was sintered at a different temperature (T s = 800 °C, 900 °C and 1000 °C) in air. In order to obtain a polycrystalline reference pattern, The crystal structures were examined by x-ray diffractometer using Cu 4 α K radiation at room temperature. The magnetic measurements were carried out with a Quantum Design superconducting quantum interference device (SQUID) MPMS system (2 ≤T≤400 K, 0 ≤ H ≤5 T). Both zero-field-cooling (ZFC) and field-cooling (FC) data were recorded. The resistance was measured by the standard four-probe method from 25 to 300 K. ACKNOWLEDGMENTS

Physica B: Condensed Matter

“…The reduction of grain size leads to a decrease in metal-insulator transition temperature. The effect of particle size on the T MÀI , magnetization and MR values have also been reported by various investigators [1,25,26].…”

Section: Transport and Magnetic Propertiesmentioning

confidence: 91%

Magnetoresistive studies on nanocrystalline La0.8Sr0.2MnO3+δ manganite

Nagabhushana¹,

Chakradhar²,

Ramesh³

et al. 2008

a b s t r a c tLow-temperature magnetoresistance (MR) measurement has been carried out on nanocrystalline La 0.8 Sr 0.2 MnO 3+d manganites prepared by combustion synthesis. This preparation method yields voluminous powders with large surface area ($40 m 2 /g) having crystalline nanosize ($50 nm) products. Formation and homogeneity of the solid solutions have been confirmed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Rietveld refinement of X-ray data indicates that as-formed compound exhibits cubic phase with space group Pm3 m. However, calcined sample transforms into rhombohedral phase with space group R-3c. The stabilization of the cubic phase in as-formed manganite is due to the substitution of Sr 2+ on La 3+ sites, resulting in higher Mn 4+ content. The low-temperature resistivity measurements down to 70 K exhibit a broad metal-insulator transition (T MÀI ) at around 257 K. MR measurements on sintered pellets show $5% MR at 1 T, whereas for 4 and 7 T, the %MR values are found as 22% and 28%, respectively, at T MÀI .