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Percolation—related magnetic coupling and magnetoresistance properties in Fe/Si1—xAgx multilayers 下载免费PDF全文
In this paper, we present a study of the magnetic coupling and magnetoresistance (MR) properties in Fe/Si1-xAgx multilayers with a granular Si1-xAgx spacer layer. We have found that, with increasing silver content (x) in a silicon matrix, the magnetic state of multilayers changes from a nonmagnetic coupling state to weak antiferromagnetic around the percolation point of the ~2.4 nm thick spacer Si1-xAgx. The MR measurements also reveal an abrupt increase of MR near the same percolation point. These changes are ascribed to the formation of the percolation path in the granular spacer. 相似文献
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固相萃取-超高效液相色谱串联质谱法同时检测禽畜粪便中多种抗生素残留 总被引:3,自引:0,他引:3
建立了固相萃取-超高效液相色谱串联质谱(SPE-UPLC/MS/MS)同时测定禽畜粪便中6种磺胺类(SAs)、4种四环素类(TCs)、3种氟喹诺酮类(FQs)、3种大环内酯类(MACs)以及1种硝基呋喃类(NFs)抗生素残留的方法。样品分别由McIlvaine-Na2EDTA缓冲液和有机混合提取液逐次超声提取,合并提取液,以正己烷去脂,过SAX-HLB固相萃取系统富集净化,经氮吹、定容后,以乙腈和0.1%甲酸-水溶液为流动相进行UPLC/MS分离检测,内标法定量。在0.1~1000μg/kg(Dry weight)浓度范围内,所有目标物标准曲线R2均大于0.99,样品加标回收率在42.3%~79.6%之间,相对标准偏差为1.4%~5.4%。方法检出限为0.1~2.0μg/kg,定量下限为0.3~6.6μg/kg。应用本方法检测华北地区多个禽畜养殖基地粪便样品32份,所有抗生素均有不同程度的检出,最高检出浓度为金霉素125μg/kg。 相似文献
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以非晶硼和氧化镍纳米颗粒为原料,在氨气中1100 oC下合成了毛刺状竹节结构的氮化硼纳米管. 利用X射线衍射和透射电镜研究了氮化硼纳米管的结构和形貌. 竹节结构纳米管表面的毛刺是六方氮化硼的纳米薄片. 提出了一种基于固态硼和气态二氧化硼扩散的毛刺形貌生长机理. 相似文献
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We have investigated the structure, optical and magnetic properties of ferroelectric KNb1-xFexO3-δ (X=0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25) synthesized by a traditional solid-state reaction method. According to the X-ray diffraction and the results of Rietveld refinement, all the samples maintain orthorhombic distorted perovskite structures with Amm2 space group without any secondary phase, suggesting the well incorporation of Fe ions into the KNbO3 matrix. With the increase of Fe concentration, the band gap of each sample is decreased gradually, which is much smaller than the 3.18 eV band gap of pure KNbO3. Through X-ray photoelectron spectrum analysis, the increased density of oxygen vacancy and Fe ions may be responsible for the observed decrease in band gap. Compared with the pure KNbO3, Fe doped samples exhibit room-temperature weak ferromagnetism. The ferromagnetism in KNb1-xFexO3-δ with low-concentration dopants (X=0.01-0.10) can be attributed to the bound magnetic polaron mediated exchange. The enhancement of magnetism for the high-concentration (X=0.10-0.20) doped samples may arise from the further increase of magnetic Fe ions. 相似文献
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以非晶硼和氧化镍纳米颗粒为原料,在氨气中1100℃下合成了毛刺状竹节结构的氮化硼纳米管. 利用X射线衍射和透射电镜研究了氮化硼纳米管的结构和形貌. 竹节结构纳米管表面的毛刺是六方氮化硼的纳米薄片. 提出了一种基于固态硼和气态二氧化硼扩散的毛刺形貌生长机理. 相似文献
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