Magnetic properties of ultrafine MnFe2O4 powders prepared by mechanochemical processing -: art. no. 184414
Magnetic properties of ultrafine MnFe2O4 powders prepared by mechanochemical processing -: art. no. 184414
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DOI：
10.1103/physrevb.63.184414
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发表时间：
2001-05-01
影响因子：
3.7
通讯作者：
Amighian, J
中科院分区：
文献类型：
--
作者：
Muroi, M;Street, R;Amighian, J
通过高能球磨活化置换反应2FeCl（3）+4MnO -> MnFe 2 O 4 + 3 MnCl 2合成了MnFe 2 O 4超细粉体。通过洗涤和磁分离从球磨或退火的粉末中除去副产物（MnCl 2）和未反应的（FeCl 3和MnO）相后，获得了具有在9.5和40 nm之间的晶粒尺寸的单相MnFe 2 O 4粉末。磁性测量结果表明，样品的自发磁化强度随晶粒尺寸的增大而减小，矫顽力随温度的降低而增大，在50 K以下，矫顽力的温度依赖性变得很强，当样品在最大磁场下冷却时，磁滞回线变得不对称，上分支的回复磁化强度和矫顽力均增强.这些意见进行了讨论，在一个模型中，它是假设每个微晶由一个亚铁磁核心包围的自旋玻璃壳和自旋的核心和壳的交换耦合。
Ultrafine MnFe2O4 powders have been synthesized via the displacement reaction 2FeCl(3)+4MnO --> MnFe2O4 + 3 MnCl2 activated by high-energy ball milling. Single-phase MnFe2O4 powders having crystallite sizes ranging between 9.5 and 40 nm have been obtained after removing the by-product (MnCl2) and unreacted (FeCl3 and MnO) phases from the as-milled or annealed powders by washing and magnetic separation. Magnetic measurements show that the spontaneous magnetization decreases with crystallite size; that the coercivity increases with decreasing temperature; and that below about 50 K the temperature dependence of coercivity becomes very strong, and the hysteresis loop becomes asymmetric with the remanent magnetization and the coercivity both enhanced in the upper branch when the sample is cooled in the maximum field. These observations are discussed in terms of a model in which it is assumed that each crystallite consists of a ferrimagnetic core surrounded by a spin-glass shell and the spins in the core and shell an exchange coupled.