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오늘 본 자료
Electron magnetic resonance (EMR) in sonochemically prepared doped nano-manganites?
A.I. Shames,E. Rozenberg,G. Gorodetsky,I. Felner,E. Sominski,G. Pang,A. Gedanken 한국물리학회 2007 Current Applied Physics Vol.7 No.1
X-band electron magnetic resonance method was explored for study of sonochemically prepared nano-powders of La-based dopedmanganites: La0.7Sr0.3MnO 3 and La0.9Ca0.1MnO 3 at 1156 T6 600 K temperature interval, including main characteristic points of itsmagnetic transitions. The data obtained were compared with those for crushed bulk single crystals of the same compositions. It is shownthat nano-powder of La0.7Sr0.3MnO 3 has the same ferromagnetic ordering as its bulk counterpart, being more homogeneous and lessanisotropic. While, nano-powder of La0.9Ca0.1MnO 3 shows two distinct ferromagnetic phases in a marked contrast to the bulk sample,where complex magnetic structure comprising canted antiferromagnetic matrix and ferromagnetic clusters is observed. To explain theobserved phenomena, the crucial role of nano-scale grain size and its interplay with spin and charge degrees of freedom in consideredsystems are discussed.
Rozenberg, E.,Shames, A. I.,Jung, G.,Mukovskii, Ya. M.,Sominski, E.,Gedanken, A.,Lee, Cheol Eui Wiley - VCH Verlag GmbH & Co. KGaA 2007 Physica status solidi. B Vol. No.
<P>Electron spin resonance was studied on three (two bulk and one nanometer sized) samples of the same La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> manganite compound aiming to compare their magnetic homogeneities. The results obtained show that both ceramic and single crystalline bulk samples are less homogeneous than nano-crystalline one. Except for higher homogeneity, the nano sample demonstrates also a weaker magnetic anisotropy. As a result, well pronounced coexistence of different magnetic phases (coexistence of ferromagnetic and paramagnetic resonance signals) is observed in bulk samples, while it is absent in nano. It is suggested that such strong difference is directly connected to the difference in structural state of the samples. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Nanometric Size Effect on Magnetic Ordering in Half-doped La0.5 Ca0.5 MnO3 Manganite: EPR Probing
M. Auslender,E. Rozenberg,A. I. Shames,D. Mogilyansky,E. Sominski,A. Gedanken,이철의 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
Measurements of the X-band electron paramagnetic resonance and the model fittings of the linewidth and intensity versus temperature dependences were employed to probe the finite-size effect on the magnetic ordering in half-doped La0.5 Ca0.5 MnO3 manganite. It is shown that complex mixed magnetic ordering in bulk samples, comprised of the antiferromagnetic and the charge-ordered (AFM/CO) component, together with the ferromagnetic one, appear to be unstable regarding this effect; the AFM/CO phase is suppressed in nano-samples, which agrees with the data of magnetic measurements. In addition, we have managed to show that the FM state, appearing in nano-grains, is frustrated due to (i) an AFM-like core-shell interaction and (ii) a strong spin disorder at the surfaces and core-shell transition layers.