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Synthesis of Granular Layers by Ion Implantation and the GMR Properties

离子注入颗粒层的合成及其 GMR 特性

基本信息

批准号：
13650355
负责人：
HAYASHI Nobuyuki
金额：
$ 2.37万
依托单位：
Kurume Institute of Technology (2002)Hosei University (2001)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

Main results are summarized as follows:1) Dose dependence of GMR effect and magnetoresistance (MR) ratio ;In the Fe/Al_2O_3 granules synthesized by ion implantation the highest MR ratio is obtained as 7.5% at the dose of 1.5×10^<17> ions/cm^2, where the α iron clusters are observed to be in critical sizes to do a transition from superparamagnetic to ferromagnetic states. Thus, superparamagnetic nanoclusters dispersed in the insulating oxide.2) Estimation of the size distribution in nano-sized Fe clusters ;The size distribution was estimated from the analysis of conversion electron Mossbauer spectra and the magnetization measurements. At the dose of 1.5×10^<17> ions/cm^2 the radii of Fe are estimated to be in wide distribution with the two peak values of 2.1 nm and 4 nm.3) Evolution of new TMR granules and treatment to improve TMR characteristics ;Fe ions are implanted into single crystals of MgO and amorphous SiO_2 to investigate the possibility of synthesizing various GMR granules. However, it is found that the MR ratios for the both nanocomposites are about 1 % at most, in contrast to Fe/Al_2O_3. However, we have found that in the implanted layers the dispersion state is altered after annealing in N_2 atmosphere at such low temperature as 550 K, which leads to the improvement of GMR properties, e.g., the increase of MR ratio to 3.5 % in Fe/MgO.5) Development of new type of alloy nanoclusters ;We have succeeded in presenting an evidence that the clusters of Fe-Co alloys can be synthesized by sequential implantation of Fe and Co ions. It is expected that the syntheses of alloy clusters by the implantation develop new fields of material science and magnetism.

主要结果如下：1）巨磁电阻效应和磁电阻率的剂量依赖性：在离子注入法制备的Fe/Al_2O_3颗粒中，当注入剂量为1.5×10^ ions/cm ^2时，磁电阻率最高，为7.5%<17>，此时α铁团簇处于临界尺寸，从超顺磁态转变为铁磁态。因此，超顺磁性纳米团簇分散在绝缘氧化物中。2）纳米Fe团簇尺寸分布的估算通过转换电子穆斯堡尔谱分析和磁化强度测量估算了纳米Fe团簇的尺寸分布。在1.5×10^<17>ions/cm ^2剂量下，Fe的半径分布较宽，有两个峰值，分别为2.1 nm和4 nm。3）新TMR颗粒的形成和改善TMR特性的处理：将Fe离子注入MgO单晶和非晶SiO_2中，研究了合成各种GMR颗粒的可能性。但是，与Fe/Al_2O_3相比，两种纳米复合材料的磁电阻率最大都在1%左右。然而，我们发现注入层在N_2气氛中550 K低温退火后，其色散状态发生了改变，从而导致了GMR特性的改善，Fe/MgO中的MR比提高到3.5%。5）新型合金纳米团簇的开发我们成功地提出了通过顺序注入Fe和Co离子可以合成Fe-Co合金团簇的证据。离子注入法合成合金团簇有望开拓材料科学和磁学的新领域。