Synthesis and Size-Dependent Exchange Bias in Inverted Core-Shell MnOMn3O4 Nanoparticles

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• 作者：German Salazar-Alvarez ; Jordi Sort ; Santiago Suriñ ; ach ; M. Dolors Bar&oacute ; Josep Nogué ; s
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：July 25, 2007
• 年：2007
• 卷：129
• 期：29
• 页码：9102 - 9108
• 全文大小：439K
• 年卷期：v.129,no.29(July 25, 2007)
• ISSN：1520-5126

文摘

Core-shell nanoparticles of MnOmages/entities/verbar.gif">Mn₃O₄ with average particle sizes of 5-60 nm, composed ofan antiferromagnetic (AFM) core and a ferrimagnetic (FiM) shell, have been synthesized and their magneticproperties investigated. The core-shell structure has been generated by the passivation of the MnO cores,yielding an inverted AFM-coremages/entities/verbar.gif">FiM-shell system, as opposed to the typical FM-coremages/entities/verbar.gif">AFM-shell. Theexchange-coupling between AFM and FiM gives rise to an enhanced coercivity of ~8 kOe and a loop shiftof ~2 kOe at 10 K, i.e., exchange bias. The coercivity and loop shift show a non-monotonic variation withthe core diameter. The large coercivity and the loop shift are ascribed to the highly anisotropic Mn₃O₄ andsize effects of the AFM (i.e., uncompensated spins, AFM domains, and size-dependent transitiontemperature).