Giant exchange bias and the vertical shifts of hysteresis loops in γ-Fe2O3-coated Fe nanoparticles
Giant exchange bias and the vertical shifts of hysteresis loops in γ-Fe2O3-coated Fe nanoparticles
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DOI：
10.1063/1.1687987
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发表时间：
2004-04
影响因子：
3.2
通讯作者：
R. Zheng;G. Wen;K. Fung;Xixiang Zhang
中科院分区：
文献类型：
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作者：
R. Zheng;G. Wen;K. Fung;Xixiang Zhang
我们制备了核/壳结构的Fe纳米粒子，其中α-Fe核直径约为5 nm，γ-Fe 2 O3壳厚约为3 nm，并对其结构和磁性进行了系统的研究。磁滞回线（M-H），在低温下测量，粒子从350 K在50 kOe的领域冷却后，在水平和垂直方向上显示出显着的位移。已经发现，交换偏置场可以高达6.3 kOe在2 K，矫顽场也大大增强了场冷却（FC）环路。低温下FC环的大交换偏置和垂直位移可能归因于壳层中的冻结自旋。提出了一个简单的模型来解释观测结果。
We fabricated core/shell-structured Fe nanoparticles, in which the α-Fe core is about 5 nm in diameter and the γ-Fe2O3 shell is about 3 nm thick, and systematically studied their structural and magnetic properties. The magnetic hysteresis (M–H) loops, measured at low temperatures, after the particles were cooled from 350 K in a 50 kOe field, show significant shifts in both horizontal and vertical directions. It has been found that the exchange-bias field can be as large as 6.3 kOe at 2 K, and that the coercive field is also enhanced greatly in the field-cooled (FC) loops. The large exchange bias and vertical shifts of the FC loops at low temperatures may be ascribed to the frozen spins in the shells. A simple model is proposed to interpret the observations.