Structure and magnetic properties of Fe nanoparticles in amorphous silica implanted with Fe ions and effect of subsequent energetic heavy ion irradiation
Structure and magnetic properties of Fe nanoparticles in amorphous silica implanted with Fe ions and effect of subsequent energetic heavy ion irradiation
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DOI：
10.1063/5.0102438
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发表时间：
2022-10
影响因子：
3.2
通讯作者：
A. Iwase;K. Fukuda;Y. Saitoh;Y. Okamoto;S. Semboshi;H. Amekura;T. Matsui
中科院分区：
文献类型：
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作者：
A. Iwase;K. Fukuda;Y. Saitoh;Y. Okamoto;S. Semboshi;H. Amekura;T. Matsui
在室温下用380 keV的Fe离子注入无定形二氧化硅（以下称为SiO2）样品。注入后，用16 MeV Au离子辐照一些样品。用SQUID磁强计研究了样品的磁性能，用透射电子显微镜和X射线吸收光谱（扩展X射线吸收精细结构和X射线吸收近边结构）研究了Fe注入SiO2样品的形貌。随着Fe注入量的增加，Fe纳米粒子的尺寸增大。部分Fe纳米粒子由Fe的氧化物组成，随着Fe注入量的增加，Fe原子的价态和Fe纳米粒子的结构逐渐接近金属α-Fe。在Fe离子注入的SiO2样品中观察到了室温磁性。用Langevin方程再现了注入少量Fe后样品的磁化强度-磁场曲线，表明Fe纳米粒子呈现超顺磁性。当Fe注入量较大时，磁化强度-磁场曲线呈现铁磁状态。这种磁性的结果与X射线吸收的结果是一致的。通过随后的16 MeV Au照射，Fe纳米颗粒被破碎，导致磁化强度降低。简要讨论了SiO2样品的光吸收特性。
Amorphous silicon dioxide (hereafter SiO2) samples were implanted with 380 keV Fe ions at room temperature. After the implantation, some samples were irradiated with 16 MeV Au ions. The magnetic property was investigated by using a SQUID magnetometer, and the morphology of Fe-implanted SiO2 samples was examined by using a transmission electron microscope and x-ray absorption spectroscopy (extended x-ray absorption fine structure and x-ray absorption near edge structure). The size of Fe nanoparticles increases with an increase in the amount of Fe implantation. A part of Fe nanoparticles consists of Fe oxides, and with an increase in the amount of Fe implantation, the valence state of Fe atoms and the structure of Fe nanoparticles gets close to those of metallic α-Fe. The room temperature magnetism was observed in Fe-implanted SiO2 samples. The magnetization–magnetic field curves for samples implanted with a small amount of Fe are reproduced by the Langevin equation, implying that Fe nanoparticles present the superparamagnetic behavior. For a large amount of Fe implantation, the magnetization–magnetic field curve shows the ferromagnetic state. Such a result of magnetic property is consistent with the results of the x-ray absorption. By the subsequent 16 MeV Au irradiation, the Fe nanoparticles were fragmentated, resulting in the decrease in magnetization. The optical absorption property of the SiO2 samples is briefly discussed.