• Title/Summary/Keyword: manganites

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Environmental Applications of Rare-Earth Manganites as Catalysts: A Comparative Study

  • Alami, D.
    • Environmental Engineering Research
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    • v.18 no.4
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    • pp.211-219
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    • 2013

  • Rare-earth manganites have a great potential for environmental applications based on their chemical and physical properties. The use of rare-earth manganites as catalysts for environmentally essential reactions was reviewed. Artificial neural networks were used to assess the catalytic activity in oxidation reactions. Relative catalytic activities of the catalysts were further discussed. We concluded that cerium manganite is the most practicable catalyst for technological purposes.

  • https://doi.org/10.4491/eer.2013.18.4.211 인용 PDF KSCI KPUBS

Dynamic heat capacity of perovskite manganites: calorimetric evidence for a first order transition and its implication to the magnetocaloric effect

  • Kim, Y. B.;Y. H. Jeong
    • Proceedings of the Korean Magnestics Society Conference
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    • 2003.06a
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    • pp.40-40
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    • 2003

  • Finding a solid material with a large value of the magnetocaloric effect near room temperature is of exceeding importance, since this would lead to the development of more compact and environmentally safer cooling systems. Recently, manganites become the focus of attention due to its large magnetocaloric effect. We demonstrate, via dynamic calorimetric measurements, that the large magnetocaloric effect in perovskite manganites stems from the first-order nature of the magnetic transition. Our results offer a clue in search for ideal magnetocaloric materials working in the vicinity of room temperature.

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Collapse of Charge Ordering in Ru-doped Mono-layered Manganites

  • Hong, Chang-Seop;Kim, Wan-Seop;Hur, Nam-Hwi
    • Journal of Magnetics
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    • v.8 no.2
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    • pp.85-88
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    • 2003

  • The magnetic and transport properties far single crystals of Ru-doped mono-layered manganites $La_{0.5}Sr_{1.5}-Mn_{1-x}Ru_xO_4$ (0$\leq$$\chi$$\leq$0.1) have been studied using neutron diffraction and magnetization measurements. Temperature dependent magnetization data reveal that with an increase in the Ru concentration the parent charge ordered antiferromagnetic state is gradually destroyed and new ferromagnetic phase evolves. In the low Ru-doped system spin glass behavior is apparent in low temperature region, which is confirmed by ac and do magnetization measurements. The competing magnetic interaction between Mn/Mn and Mn/Ru couples is the most likely cause of the spin glass transition.

  • https://doi.org/10.4283/JMAG.2003.8.2.085 인용 PDF KSCI

Improved Magnetic Anisotropy of YMn1-$xCrxO_3 $ Compounds

  • Yoo, Y.J.;Park, J.S.;Kang, J.H.;Kim, J.;Lee, B.W.;Kim, K.W.;Lee, Y.P.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.218-218
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    • 2012

  • Recently, hexagonal manganites have attracted much attention because of the coexistence of ferroelectricity and antiferromagnetic (AFM) order. The crystal structure of hexagonal manganites consists of $MnO_5$ polyhedra in which $Mn^{3+}$ ion is surrounded by three oxygen atoms in plane and two apical oxygen ions. The Mn ions within Mn-O plane form a triangular lattice and couple the spins through the AFM superexchange interaction. Due to incomplete AFM coupling between neighboring Mn ions in the triangular lattice, the system forms a geometrically-frustrated magnetic state. Among hexagonal manganites, $YMnO_3$, in particular, is the best known experimentally since the f states are empty. In addition, for applications, $YMnO_3$ thin films have been known as promising candidates for non-volatile ferroelectric random access memories. However, $YMnO_3$ has low magnetic order temperature (~70 K) and A-type AFM structure, which hinders its applications. We have synthesized $YMn1_{-x}Cr_xO_3$ (x = 0, 0.05 and 0.1) samples by the conventional solid-state reaction. The powders of stoichiometric proportions were mixed, and calcined at $900^{\circ}C$ for $YMn1_{-x}Cr_xO_3$ for 24 h. The obtained powders were ground, and pressed into 5-mm-thick disks of 1/2-inch diameter. The disks were directly put into the oven, and heated up to $1,300^{\circ}C$ and sintered in air for 24 h. The phase of samples was checked at room temperature by powder x-ray diffraction using a Rigaku Miniflex diffractometer with Cu $K{\alpha}$ radiation. All the magnetization measurements were carried out with a superconducting quantum-interference-device magnetometer. Our experiments point out that the Cr-doped samples show the characteristics of a spin-glass state at low temperatures.

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