Synthesis of iron based alloy nanoparticles by ion implantation and the magnetic properties.

金属-绝缘体纳米复合材料层通过高剂量注入磁性离子到绝缘氧化物中合成，提供了有吸引力的结构，如巨型磁性隧道结。用100 keV Fe^+离子注入α-Al_2O_3单晶，观察到了显著的隧道磁电阻（TMR）效应，注入层的磁电阻率约为7 ~ 8%。所得结果比用射频溅射法制备的Fe/Al_2O_3颗粒膜的结果大一倍左右。此外，我们还成功地用Fe和Co离子顺序注入的方法在Al_2O_3基体中合成了FeCo合金纳米团簇。在FeCo颗粒层中也证明了合金化导致铁磁矩的增加。结果表明，在室温下，磁电阻比可望提高到10%以上，通过这些研究，我们获得了有关注入的聚结状态的详细信息 ...更多信息 Fe离子的转换电子穆斯堡尔谱（CEMS）。CEMS为这种表征提供了原子尺度上的高度灵敏和微观的手段，特别是当它与质量选择的Fe注入相结合时<57>。在实验中，我们报道了<57><59>在Al_2O_3基体中注入~（40）Fe和~（40）Co离子，改变注入量，可显著提高TMR效应，并在室温下获得了Fe、Co和FeCo颗粒膜中最大的MR比。此外，<57><63>在室温下进行了~（40）Fe和~（40）Cu离子的注入，注入总剂量为1.5×10 ~（40）<17>ions/cm ~ 2，注入能量为74-105 keV。CEMS和掠射角X射线衍射（GXRD）的测量结果表明，Fe离子注入SiO_2衬底后，Si原子溶解在沉淀的Fe纳米团簇中。此外，Cu离子的加入促进了Fe/Al_2O_3和Fe/SiO_2颗粒从超顺磁性向铁磁性的转变，形成了亚稳态的Fe-Cu合金纳米团簇。少

Metal-insulator nanocomposite layers synthesized by high dose implantation of magnetic ions into insulating oxides provide attractive structures such as giant magnetic tunneling junctions. An eminent tunneling magnetoresistance (TMR) effect was observed in α-Al_2O_3 single crystals implanted with 100 keV Fe^+ ions, where the implanted layers exhibit a magnetoresitance (MR) ratio of about 7〜8%. The obtained value is about twice as large as that observed for similar granular Fe/Al_2O_3 films prepared by rf sputtering. Furthermore, we have succeeded in synthesizing nanosizedclusters of FeCo alloys in the Al_2O_3 matrices by sequential implantation of Fe and Co ions. It was also demonstrated in the FeCo granular layers that the alloying leads to an increase of the iron magnetic moment. From the result it is expected for the MR ratio to increase to a value of more than 10% at room temperature.Through these studies we have obtained detailed information on the aggregation states of implanted … More Fe ions by means of conversion electron Mossbauer spectroscopy (CEMS). CEMS provides highly sensitive and microscopic means in atomic scale for such characterization especially when it is combined with the mass-selected ^<57>Fe implantation. In the studies we have reported an eminent enhancement of TMR effect by changing the relative amount of ^<57>Fe and ^<59>Co ions implanted in Al_2O_3 matrices with an energy of 100 keV and presented the largest MR ratio at room temperature among the values reported in the Fe-, Co-, and FeCo granular films.Furthermore, the implantation of ^<57>Fe and ^<63>Cu ions was performed at room temperature up to a total dose of 1.5×10^<17> ions/cm^2 with projectiles energies of 74-105 keV. It is shown by the measurements of CEMS and glancing angle X-ray diffraction (GXRD) that Fe implantation into SiO_2 substrate results in the dissolution of Si atoms into the precipitated iron nano-clusters. Furthermore, it is shown that the addition of Cu ions into both Fe/Al_2O_3 and Fe/SiO_2 granules promotes the transition from superparamagnetic to ferromagnetic states, indicating the formation of metastable Fe-Cu alloy nanoclusters. Less