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X-ray diffraction and magnetic properties measurement of nanopowder (La[0.7]Sr[0.3])[0.9]Mn[1.1]O[3] manganite

Bażela-Wróbel W., Dyakonov W., Dul M.

Czasopismo Techniczne. Nauki Podstawowe

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2009

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R. 106, z. 1-NP

123-137

EN

We report on the X-ray powder diffraction and magnetic measurements of nanosize (La[0.7]Sr[0.3])[0.9]Mn[1.1]O[3] manganite. The nanoparticles were synthesized with use of co-precipitation method at different (800, 900 and 950[degrees]C) temperatures. Their crystal structure was determined to be perovskite-like with a rhombohedral distortion (the space group R 3c). The phase composition and specific surface nanopowders were determined. The average size of synthesized nanoparticles (from 32 to 88 nm) was estimated by both the method of low temperature adsorption of argon and X-ray diffraction measurements. All the nanosize samples show ferromagnetic-like ordering with close phase transition temperatures. Their magnetization decreases with reducing the particle size. The decrease of magnetization with decreasing particle size is due to increasing the surface contribution to magnetization. The magnetic entropy was shown to increase with increasing applied magnetic field and to be smaller for the small particles.

PL

W artykule przedstawiono wyniki pomiarów dyfrakcji rentgenowskiej oraz uzyskanych metodą magnetometryczną nanorozmiarowego manganitu (La[0.7]Sr[0.3])[0.9]Mn[1.1]O[3]. Próbki otrzymano metodą zol-żel w następujących temperaturach: 800, 900 i 950[stopni]C. Wszystkie próbki krystalizują w układzie romboedrycznym (grupa przestrzenna R 3c). Średni rozmiar ziaren (od 32 do 88 nm) określono za pomocą rentgenowskiej dyfrakcji proszkowej oraz metodą niskotemperaturowej adsorpcji argonu. Wszystkie próbki wykazują ferromagnetyczne uporządkowanie z bliskimi temperaturami przejścia fazowego i ich namagnesowanie maleje wraz ze zmniejszaniem się rozmiarów ziaren. Zmniejszenie namagnesowania wraz ze zwiększaniem się rozmiarów ziaren jest spowodowane wzrostem wkładu powierzchni ziaren do namagnesowania. Magnetyczna entropia rośnie wraz ze wzrostem pola magnetycznego i jest mniejsza dla małych ziaren.

2

Elastic properties of double layered manganite La1.2Sr1.8-xCaxMn2O7 (x = 0.0-0.4)

Reddy Y. S., Ramana Reddy M. V., Veerasomaiah P., Vishnuvardhan Reddy C.

Materials Science Poland

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2007

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Vol. 25, No. 3

619--626

EN

Polycrystalline bulk samples of double layered manganite system La1.2Sr1.8-xCaxMn2O7 (x = 0.0-0.4) have been synthesized by the sol-gel method. Based on powder X-ray diffraction, it has been found that their lattice parameters decrease with increasing Ca content. The elastic behaviour of the system has been investigated at ~300 K employing ultrasonic pulse transmission technique at 1 MHz. The values of elastic moduli and acoustic Debye temperatures have been computed from the longitudinal and shear wave velocities. The measured values of elastic moduli have been corrected to zero porosity using various correction methods. The variation of elastic moduli with Ca content is interpreted in terms of the strength of interatomic bonding.

3

Magnetic thin films and nanostructures for emerging technologies.

Krishnan K.M.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

775-778

EN

The optimization of the magnetic properties of materials for a wide range of technologies requires a dynamic iteration between synthesis, property measurements and the evaluation/control of microstructure (physical, chemical & magnetic) at the appropriate length scales. In addition, atomically engineered thin films and nanostructures offer new opportunities to elucidate the physics of magnetism, test new theories and most importantly build new materials with unique anisotropy, transport and hysteretic properties. These interests arise from advances in materials synthesis, an increased appreciation of the degree to which magnetic properties are influenced by microstructure and interfacial processes and the ability to characterize them by electron-optic and x-ray scattering/dichroism techniques. In this paper, we present an overview of our recent work in these areas, involving an integrated approach of growth/synthesis, property measurements and advanced characterization.