Structure and Properties of Nonstoichiometric La1 – xNaxMnO3 ±  Solid Solutions

Yanchevskiĭ, O. Z.; Tovstolytkin, A. I.; V’yunov, O. I.; Durilin, D. A.; Belous, A. G.

doi:10.1023/b:inma.0000034775.17532.f2

Cited by 19 publications

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“…To clarify the picture, one should carry out a comprehensive analysis of the ESR spectra on the carefully characterized samples with a broadened magnetic transition. As follows from the studies of magnetic properties, the most suitable samples for this aim are Ca-and Na(K)-doped lanthanum manganites, the peculiar feature of which is a wide temperature range of the PM and FM phases coexistence [14][15][16][17]. Here, we present the results of the ESR measurements in (Ca,Na)-doped lanthanum manganites, which clearly show that coexisting phases cannot be considered as independent and their mutual influence should be taken into account.…”

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“…To do this, the bulk polycrystalline samples with the nominal chemical formula La 0.7+x Ca 0.3-2x Na x MnO 3 were prepared, where the substitution was made according to the scheme 2Ca → La + Na. The reason for the vacancy formation was enhanced sodium volatility at high temperatures [15]. The details of the samples' preparation and characterization are described in Refs.…”

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“…The details of the samples' preparation and characterization are described in Refs. 15,16,18. The ESR investigations were performed on the powdered samples with x = = 0.04 and 0.08.…”

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Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Tovstolytkin

Pogorily

Podyalovskii

2009

Low Temperature Physics

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The analysis of the ESR spectra for the powdered samples of (Ca,Na)-doped manganites have been performed in the temperature range 220-320 K. It is shown that the samples under investigation are characterized by a broadened para-to ferromagnetic transition and complicated spectra within the transitional region. The conclusion is made that the satisfactory interpretation of the resonance data is only possible if the interference of the coexisting phases is taken into account within the transitional region. Under these conditions, the resonance field for the paramagnetic phase is shown to increase with the temperature lowering, while that for the ferromagnetic phase first decreases and then approaches a value characteristic of the uniformly magnetized ferromagnetic sample. It is noted that the results obtained are in compliance with those predicted theoretically for the spherical particles containing a mixture of the paramagnetic and ferromagnetic phases. Electrically conducting ferromagnetic materials where the conduction electrons have a high mobility and are fully spin-polarized are desirable for realizing thin-film spin electronic devices [1,2]. The doped manganite systems La 1-x M x MnO 3 (M = alkaline or alkaline earth element), due to their half-metallic ferromagnetic nature and the concomitant complete spin polarization, have been considered as very promising materials for the creation of spin emitters and filters in magnetic nanostructures. PACSRecent theoretical and experimental studies have shown that the essential physics of doped manganites stems from a strongly pronounced tendency towards magnetic phase separation, which often makes an inhomogeneous state more preferable than a homogeneous one [3][4][5]. Electron spin resonance (ESR) is an advantageous tool to probe the manganite behavior within the regions of phase coexistence but the interpretation of the results is far from being unambiguous [6][7][8]. It is the mutual influence of coexisting phases that may strongly change the resonance conditions for each of the coexisting phases [6,9,10].The analysis of the behavior of the system in which paramagnetic (PM) and ferromagnetic (FM) phases coexist over a wide temperature range was carried out in Refs. 6 and 10. Drastic transformations of the resonance spectra are predicted for the region of the phase coexistence. The fact that the FM phase doesn't occupy the whole volume of a particle changes the resonance conditions for the FM phase, as they in the first place are governed by the shape of FM regions [11]. On the other hand, the magnetic fields created by the FM regions strongly transform the resonance conditions for the PM phase [6,10].To date, there have been only few works with the reasonable interpretation of experimental data within the temperature range where the FM and PM phases coexist [6,9,12,13]. To clarify the picture, one should carry out a comprehensive analysis of the ESR spectra on the carefully characterized samples with a broadened magnetic transition. As follows from the studies of...

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Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Tovstolytkin

Pogorily

Podyalovskii

2009

Low Temperature Physics

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“…Such difference is often attributed to the grain boundary effects [18,19]. Other studies suggest that the doping level in the A-site [20] as well as oxygen deficiency [19,21] play an important role for the observed electrical behaviour. 1.5H 2 O for higher Na doping rate.…”

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Synthesis, structural, magnetic and electrical properties of nominal La_0.67Ba_0.33-xNa_xMnO₃(0 ≤ x ≤ 0.33) manganites

Hcini

Zemni

Boudard

et al. 2012

EPJ Web of Conferences

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Abstract.Complete nominal solid solutions La 0.67 Ba 0.33-x Na x MnO 3 (0 ≤ x ≤ 0.33) have been elaborated by ceramic route at 1200°C. ICPAES chemical analysis and XRD Rietveld structure refinement revealed that the nominal Na content is not achieved by our ceramic method. The chemical formula should be rather written as La α Ba β Na λ MnO 3-δ with a significantly lower Na content (λ), than the nominal one (x), and with a slight deficit (δ) in oxygen content, leading to the appearance of two minor secondary phases identified as Mn 3 O 4 and Na 0.55 Mn 2 O 4 . 1.5H 2 O. Magnetization and electrical resistance vs. temperature show paramagnetic/semiconductor -ferromagnetic/metallic transitions with only a slight decrease in magnetic and electrical transition temperatures when Na content increases. Such amount of this decrease is not expected according to the nominal Na content giving a significant difference between nominal and experimental Mn 4+ /Mn 3+ ratios.

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“…The target was synthesized by means of the standard solid-phase reaction method [17]. The films 250 nm in thickness were deposited on aAl 2 O 3 polycrystalline substrates held at 300 8C in an atmosphere consisting of a mixture of argon (30%) and oxygen (70%).…”

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Mixed magnetic state of sodium‐doped manganites and its transformation in the course of para‐ to ferromagnetic transition

Dzyublyuk

Tovstolytkin

Pogorily

2011

Materialwissenschaft Werkst

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The features of the transformation of the mixed magnetic state in the course of a para-to ferromagnetic transition have been specified for the thin films of sodium-doped lanthanum manganites, by means of electron spin resonance measurements. It was found that the process of the ferromagnetic phase nucleation is spatially non-uniform and includes a few successive stages upon lowering temperature. At the first step, the regions with a shape close to oblate spheroids are formed in a paramagnetic matrix. The next step includes the formation of the spheroids elongated perpendicular to a film plane, and finally, all these entities merge together to form continuous ferromagnetic regions. It is concluded that the second kind of ferromagnetic nuclei is likely to be related to the isolated crystallites, which are characterized by weakened exchange interactions.Keywords: sodium-doped manganites / mixed magnetic state / magnetic transition / Die Umwandlung gemischter magnetischer Zustände von Natrium-dotierten Manganiten im Hinblick auf den Übergang von Para-zu Ferromagnetismus wurde an dünnen Filmen aus Natrium-dotierten Lanthanmanganiten mittels Elektronspin-Resonanz untersucht. Es wurde gefunden, dass der Prozess der ferromagnetischen Phasennukleation räumlich nicht einheitlich ist und einige schrittweise Stufen bei niedrigeren Temperaturen einschließt. Bei der ersten Stufe werden die Regionen mit einer Form nahe an abgeflachten Sphäroiden in einer paramagnetischen Matrix geformt. Die nächste Stufe schließt die Bildung von Sphäroiden ein, die gestreckt in Richtung der Filmebene sind. Schließlich verschmelzen diese Formen und bilden kontinuierliche ferromagnetische Regionen. Die zweite Art der ferromagnetischen Kerne ist wahrscheinlich mit den isolierten Kristalliten verbunden, die durch eine schwache Austauschwechselwirkung charakterisiert sind.

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Structure and Properties of Nonstoichiometric La_{1 – x}Na_xMnO_{3 ±}Solid Solutions

Cited by 19 publications

References 12 publications

Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Synthesis, structural, magnetic and electrical properties of nominal La_0.67Ba_0.33-xNa_xMnO₃(0 ≤ x ≤ 0.33) manganites

Mixed magnetic state of sodium‐doped manganites and its transformation in the course of para‐ to ferromagnetic transition

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Structure and Properties of Nonstoichiometric La1 – xNaxMnO3 ± Solid Solutions

Cited by 19 publications

References 12 publications

Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites

Synthesis, structural, magnetic and electrical properties of nominal La0.67Ba0.33-xNaxMnO3(0 ≤ x ≤ 0.33) manganites

Mixed magnetic state of sodium‐doped manganites and its transformation in the course of para‐ to ferromagnetic transition

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Product

Resources

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Structure and Properties of Nonstoichiometric La_{1 – x}Na_xMnO_{3 ±}Solid Solutions

Synthesis, structural, magnetic and electrical properties of nominal La_0.67Ba_0.33-xNa_xMnO₃(0 ≤ x ≤ 0.33) manganites