Nanometer Size Effect on Magnetic Properties of Sm0.8Ca0.2MnO3 Nanoparticles

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• 作者：Vladimir Markovich ; Ivan Fita ; Andrzej Wisniewski ; Roman Puzniak ; Dmitrii Mogilyansky ; Przemyslaw Iwanowski ; Piotr Dluzewski ; Gad Gorodetsky
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：January 12, 2012
• 年：2012
• 卷：116
• 期：1
• 页码：435-447
• 全文大小：1369K
• 年卷期：v.116,no.1(January 12, 2012)
• ISSN：1932-7455

文摘

Magnetic properties of compacted Sm_0.8Ca_0.2MnO₃ (SCMO) particles with average particle size of 23鈥?00 nm, prepared by the glycine-nitrate method, have been investigated. It was found that the relative volume of the ferromagnetic phase decreases with decreasing particle size. Curves of field-cooled and zero-field-cooled magnetization (M_ZFC) exhibit a bifurcation just below the Curie temperature, T_C^dc 鈮?55鈥?4 K, determined from magnetization measurements for all particles studied. The field dependence of M_ZFC peak shows reasonable agreement with both the de Almeida鈥揟houless H^2/3 line and the H² power law. Measurements of ac susceptibility in the temperature range 5鈥?00 K and the frequency range f = 10 Hz to 10 kHz show a sharp peak for both real and imaginary components in the vicinity of T_C^dc, apparently attributed to the Hopkinson effect. The Curie temperature determined by zeroing the imaginary part of ac susceptibility 蠂鈥?T) shows a larger value of T_C 鈮?85鈥?0 K in compliance with T_C of bulk Sm_0.8Ca_0.2MnO₃ sample. A second small peak in ac susceptibility at T 鈮?11鈥?5 K is seemingly associated with antiferromagnetic or ferrimagnetic ordering. Although for smaller particles both peaks depend on frequency, no shift to higher temperatures with increasing f, characteristic for spin-glass (SG) systems, was observed. Smallest, 23 nm, SCMO particles exhibit 鈥渨aiting time鈥?dependence in time evolution of M_ZFC, a feature expected for SG. These particles do not show any memory effects in M_ZFC, which is in strong contrast with the usual behavior exhibited by ferromagnetic nanoparticles with strong enough interparticle interaction. The dissimilarity in magnetic properties and dynamic characteristics observed for SCMO and for La_0.8Ca_0.2MnO₃ nanoparticles is discussed, taking into account a difference in the width of the band and the strength of double exchange and interparticle interactions.