Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film

Perovskite manganites oxide materials have attracted much attention due to their promising potential applications in the magnetic sensor or devices. In this research, La1-xAxMnO3 (x = 0.33 when A=Ca, Sr and Ba; x= 0.2 when A=Na and K) in bulk form were prepared via solid state reaction method. La0.6...

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Main Author:	Ng, Siau Wei
Format:	Thesis
Language:	English English
Published:	2011
Subjects:	Perovskite - Structures Perovskite - Electric properties Perovskite - Magnetic properties
Online Access:	http://psasir.upm.edu.my/id/eprint/26978/1/FS%202011%2088R.pdf
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spelling	my-upm-ir.269782022-01-26T05:43:59Z Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film 2011-03 Ng, Siau Wei Perovskite manganites oxide materials have attracted much attention due to their promising potential applications in the magnetic sensor or devices. In this research, La1-xAxMnO3 (x = 0.33 when A=Ca, Sr and Ba; x= 0.2 when A=Na and K) in bulk form were prepared via solid state reaction method. La0.67Sr0.33MnO3 (LSMO) and La0.8Na0.2MnO3 (LNMO) are then converted to thin film via pulse laser deposition method (PLD) on different substrates (corning glass, fused silica glass and MgO (100)) and deposition duration. Rietveld refinement of X-ray diffraction data showed that all samples are polycrystalline having trigonal crystal structure except for La0.67Ca0.33MnO3 (LCMO) and La0.67Ba0.33MnO3 (LBMO) which are orthorhombic. From the Rietveld refinement, we observed that the lattice parameter, Mn-O bond length and bond angle changed in thin film which were influenced by the substrates type and deposition duration. The thickness of films was in the range of ~0.3-3.0 μm. The crystallite size for the thin film is between 15-22 nm. The grain size distribution for bulk samples are around 1.0-2.0 μm. A huge change of surface microstructure can be observed for thin film samples, where the grain size is reduced to ~50-150 nm. Some nano-crack effects were observed in the thin film samples where this effect is due to the different coefficient of thermal expansion between the film and substrates during the annealing process. Thin film samples showed a much higher resistance (about 2-3 orders) due to the existence of disordered phase at the grain boundary and/or nano-crack barrier that causes higher scattering and/or tunneling effect when the electrons pass through them. The metal-insulator temperature (Tp) for LSMO shifted to lower values in the thin films, probably due to the change of Mn-O bond length and bond angle. Conversely, LNMO system showed greater Tp value in thin film suggesting that the grain boundary effect might also contribute to the Tp changes. Nonetheless, the deposition duration and substrates used also influence the Tp value. Overall, negative magnetoresistance (MR) have been obtained for bulk and thin films. The MR value increases with decreasing temperature at low applied magnetic field which known as Low Field Magnetoresistance (LFMR). In thin film form the %MR value has been improved with -25% for LS_M15 and -22% for LN_M20 as compared to that of the bulk LSMO (-16%) and LNMO (-21%) when a magnetic field of 1 Tesla was applied at 90 K. Perovskite - Structures Perovskite - Electric properties Perovskite - Magnetic properties 2011-03 Thesis http://psasir.upm.edu.my/id/eprint/26978/ http://psasir.upm.edu.my/id/eprint/26978/1/FS%202011%2088R.pdf application/pdf en public masters Universiti Putra Malaysia Perovskite - Structures Perovskite - Electric properties Perovskite - Magnetic properties Faculty of Science English
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English English
topic	Perovskite - Structures Perovskite - Electric properties Perovskite - Magnetic properties
spellingShingle	Perovskite - Structures Perovskite - Electric properties Perovskite - Magnetic properties Ng, Siau Wei Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
description	Perovskite manganites oxide materials have attracted much attention due to their promising potential applications in the magnetic sensor or devices. In this research, La1-xAxMnO3 (x = 0.33 when A=Ca, Sr and Ba; x= 0.2 when A=Na and K) in bulk form were prepared via solid state reaction method. La0.67Sr0.33MnO3 (LSMO) and La0.8Na0.2MnO3 (LNMO) are then converted to thin film via pulse laser deposition method (PLD) on different substrates (corning glass, fused silica glass and MgO (100)) and deposition duration. Rietveld refinement of X-ray diffraction data showed that all samples are polycrystalline having trigonal crystal structure except for La0.67Ca0.33MnO3 (LCMO) and La0.67Ba0.33MnO3 (LBMO) which are orthorhombic. From the Rietveld refinement, we observed that the lattice parameter, Mn-O bond length and bond angle changed in thin film which were influenced by the substrates type and deposition duration. The thickness of films was in the range of ~0.3-3.0 μm. The crystallite size for the thin film is between 15-22 nm. The grain size distribution for bulk samples are around 1.0-2.0 μm. A huge change of surface microstructure can be observed for thin film samples, where the grain size is reduced to ~50-150 nm. Some nano-crack effects were observed in the thin film samples where this effect is due to the different coefficient of thermal expansion between the film and substrates during the annealing process. Thin film samples showed a much higher resistance (about 2-3 orders) due to the existence of disordered phase at the grain boundary and/or nano-crack barrier that causes higher scattering and/or tunneling effect when the electrons pass through them. The metal-insulator temperature (Tp) for LSMO shifted to lower values in the thin films, probably due to the change of Mn-O bond length and bond angle. Conversely, LNMO system showed greater Tp value in thin film suggesting that the grain boundary effect might also contribute to the Tp changes. Nonetheless, the deposition duration and substrates used also influence the Tp value. Overall, negative magnetoresistance (MR) have been obtained for bulk and thin films. The MR value increases with decreasing temperature at low applied magnetic field which known as Low Field Magnetoresistance (LFMR). In thin film form the %MR value has been improved with -25% for LS_M15 and -22% for LN_M20 as compared to that of the bulk LSMO (-16%) and LNMO (-21%) when a magnetic field of 1 Tesla was applied at 90 K.
format	Thesis
qualification_level	Master's degree
author	Ng, Siau Wei
author_facet	Ng, Siau Wei
author_sort	Ng, Siau Wei
title	Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
title_short	Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
title_full	Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
title_fullStr	Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
title_full_unstemmed	Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film
title_sort	structural, magnetic and electrical properties of la-a-mn-o (a=ca, sr, ba, na and k) in bulk and thin film
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Science
publishDate	2011
url	http://psasir.upm.edu.my/id/eprint/26978/1/FS%202011%2088R.pdf
_version_	1747811564657836032

Structural, magnetic and electrical properties of La-A-Mn-O (A=Ca, Sr, Ba, Na and K) in bulk and thin film

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