Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK.
J Phys Condens Matter. 2013 Sep 25;25(38):386004. doi: 10.1088/0953-8984/25/38/386004. Epub 2013 Aug 29.
We have investigated atomic structure and magnetism in Fe nanoparticles with a diameter of 2 nm embedded in a Pd matrix. The samples for these studies were prepared directly from the gas phase by co-deposition, using a gas aggregation source and an MBE-type source for the Fe nanoparticles and Pd matrix respectively. Extended absorption fine structure (EXAFS) measurements indicate that there is an appreciable degree of alloying at the nanoparticle/matrix interface; at dilute nanoparticle concentrations, more than half of the Fe atoms are alloyed with Pd. This leads to a core/shell structure in the embedded nanoparticles, with an FexPd1-x shell surrounding a reduced pure Fe core. Magnetism in the nanocomposite samples was probed by means of magnetometry measurements, which were interpreted in the light of their atomic structure. These point to a magnetized cloud of Pd atoms surrounding the embedded nanoparticles which is significantly larger than around single Fe atoms in Pd. The coercivities in the Fe/Pd nanocomposite samples are larger than in FexPd1-x atomic alloys of corresponding composition, which is consistent with exchange coupling between the magnetically harder and softer regions in the nanocomposite samples.
我们研究了嵌入 Pd 基质中的直径为 2nm 的 Fe 纳米颗粒的原子结构和磁性。这些研究的样品是通过气相共沉积直接从气相制备的，分别使用气体团聚源和 MBE 型源作为 Fe 纳米颗粒和 Pd 基质的源。扩展吸收精细结构（EXAFS）测量表明，在纳米颗粒/基质界面处存在相当程度的合金化；在稀纳米颗粒浓度下，超过一半的 Fe 原子与 Pd 合金化。这导致嵌入纳米颗粒中存在核/壳结构，其中 FexPd1-x 壳围绕还原的纯 Fe 核。通过磁强计测量研究了纳米复合材料样品中的磁性，根据其原子结构对其进行了解释。这些结果表明，在嵌入的纳米颗粒周围存在一个围绕 Pd 原子的磁化云，其尺寸明显大于围绕 Pd 中的单个 Fe 原子的磁化云。Fe/Pd 纳米复合材料样品中的矫顽力大于具有相应组成的 FexPd1-x 原子合金的矫顽力，这与纳米复合材料样品中磁硬区和软区之间的交换耦合一致。
