Magnetic characterization of noninteracting,randomly oriented,nanometer-scale ferrimagnetic particles

作     者：Changqian Cao,Lanxiang Tian,Qingsong Liu,Weifeng Liu,Guanjun Chen, and Yongxin Pan 1 Paleomagnetism and Geochronology Laboratory,Key Laboratory of the Earth’s Deep Interior,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,China. 2 Also at France-China Bio-Mineralization and Nano-Structures Laboratory,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,China. 3 Also at Graduate University of Chinese Academy of Sciences,Beijing, China. 4 State Key Laboratory of Microbial Technology,School of Life Sciences,Shandong University,Jinan,China. 

会议名称：《中国科学院地质与地球物理研究所第十届(2010年度)学术年会》

会议日期：2011年

学科分类：07[理学] 070205[理学-凝聚态物理] 08[工学] 080501[工学-材料物理与化学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：supported by the Chinese Academy of Sciences projects and the National Natural Science Foundation of China grant 40821091 the CAS/SAFEA International Partnership Program for Creative Research Teams 

摘      要：[1]Studying the magnetic properties of ultrafine nanometer-scale femmagnetic particles (10 nm)is vital to our understanding of superparamagnetism and its applications to environmental magnetism,biogeomagnetism,iron biomineralization,and biomedical ***,magnetic properties of the ultrafine nanometer-sized femmagnetic grains are very poorly constrained because of ambiguities caused by particle magnetostatic interactions and unknown size *** resolve these problems,we synthesized magnetoferritins using the recombinant human H chain ferritin(HFn). These femmagnetic HFn were further purified through size exclusion chromatography to obtain monodispersed ferrimagnetic *** electron microscopy revealed that the purified ferrimagnetic HFn are monodispersed and each consists of an iron oxide core(magnetite or maghemite)with an average core diameter of 3.9±1.1 nm imbedded in an intact protein *** R value of the Wohlfarth-Cisowski test measured at 5 K is 0.5,indicating no magnetostatic *** saturation isothermal remanent magnetization acquired at 5 K decreased rapidly with increasing temperature with a median unblocking temperature of 8.2 *** preexponential frequency factor f determined by AC susceptibility is(9.2±7.9)×*** extrapolated M/M and B/B at 0 K are 0.5 and 1.12,respectively,suggesting that the ferrimagnetic HFn cores are dominated by uniaxial *** calculated effective magnetic anisotropy energy constant K=1.2×10 J/m,which is larger than previously reported values for bulk magnetite and/or maghemite or magnetoferritin and is attributed to the effect of surface *** data provide useful insights into superparamagnetism as well as biomineralization of ultrafine ferrimagnetic particles.