Au掺杂对CoPt纳米颗粒结构和磁性的影响

关键词:CoPt; Au; 溶胶-凝胶; 磁性; 尺寸

DOI:10.13877/j.cnki.cn22-1284.2015.10.014

收稿日期：2015-07-29

基金项目：国家自然科学

作者简介：张小龙，男，吉林四平人，助理实验师，硕士.

通讯作者：王雅新，女，吉林四平人，教授，博士，硕士生导师.

中图分类号：0482.54文献标志码：A

CoPt(FePt)磁性纳米材料在药物靶向治疗，磁存储等多个领域具有潜在的应用价值[1-9].其中，CoPt纳米材料以其较好的热稳定性、抗氧化性和抗腐蚀性等优点而备受青睐[10，11].当CoPt磁性纳米材料的化学成分不同时，其具有不同的结构相，例如：面心四方结构(FCT)的L10相, L11相, L12相, 面心立方结构(FCC)相，且具有不同结构相的CoPt纳米材料在不同领域均有应用[12，13].早期制备的CoPt纳米材料磁性较小，且制备方法复杂，有毒，已经不能满足现阶段磁存储对于存储介质的需求[14-21].为了满足磁存储的需求，进一步提高CoPt纳米材料的磁性，以及限制其颗粒尺寸的增长，部分研究学者在制备CoPt纳米材料过程中添加其它元素，例如C, Ag, Cu, Si等[21-25].本文主要是利用溶胶-凝胶法合成CoPt, CoPt-Au纳米颗粒，利用XRD，TEM，VSM等测试手段对样品进行了系统的结构与性能表征.

1实验

实验原料：六水合氯铂酸(H2PtCl6·6H2O),六水合硝酸钴(Co(NO3)2· 6H2O),一水合柠檬酸(C6H8O7·H2O)以及四氯金酸(HAuCl4)等试剂.实验具体步骤为：按照一定的摩尔比例称取试剂，将试剂混合搅拌一段时间，得到混合液，混合液经过搅拌，干燥，最后在氩气气氛下进行热处理1小时，即可制备出有序的L10相CoPt纳米颗粒.

2结果与讨论

图1为样品的XRD图谱.图1可以看出样品CoPt, CoPt-Au纳米颗粒均形成(001)，(110),(111),(200),(002),(201),(112),(220)以及(202)晶格峰,不含有其它的杂质峰，说明样品CoPt,CoPt-Au形成了纯相的面心四方结构CoPt纳米颗粒.样品CoPt-Au的XRD图谱中，存在Au的(111),(200),(220)衍射峰，说明样品CoPt-Au中含有Au单质.为了进一步验证Au掺杂对样品的影响，我们利用公式S=[1-(c/a)]/[1-(c/a)th][26](S为样品的有序度，(c/a)为样品的实验值(c/a)th为样品的理论值，其中a,c为样品的晶格参数)对样品的有序度进行分析，分析结果显示，样品CoPt和CoPt-Au的有序度分别为0.94和0.96,这一结果说明Au元素掺杂提高了CoPt纳米颗粒的有序度.我们利用谢乐公式：L=0.89λ/βcosθ(L,λ，β，θ分别为样品的尺寸，X射线的入射波长为0.15406nm，布拉格衍射角，衍射峰的半高宽)对样品CoPt,CoPt-Au纳米颗粒进行了尺寸分析，样品CoPt、CoPt-Au的平均颗粒尺寸分别为16nm、20nm左右.谢乐公式结果表明，Au元素掺杂促进了CoPt纳米颗粒的尺寸增长.

图1　CoPt,CoPt-Au纳米颗粒的XRD图谱

图2为样品CoPt(a), CoPt-Au(b)纳米颗粒的TEM形貌图.TEM结果显示，样品CoPt, CoPt-Au均呈现椭球形，样品CoPt-Au较CoPt团聚现象明显.此外，样品CoPt-Au的颗粒平均尺寸大于CoPt的颗粒尺寸，这一结果与Nandwana等人研究的结果相似[27],同时与XRD结果相对应.

图2　CoPt, CoPt-Au纳米颗粒的TEM图

图3为样品CoPt, CoPt-Au纳米颗粒的磁滞回线图.从图3可以看出，各样品的矫顽力大小依次为4970 Oe、6410 Oe，这说明Au元素的掺杂能够提高CoPt纳米颗粒的矫顽力，且样品CoPt-Au的饱和磁化强度(Ms)较样品CoPt的饱和磁化强度(Ms)小，参照XRD结果表明，这可能由样品CoPt-Au的有序度较样品CoPt的有序度大引起的.

3结论

本文利用改进的溶胶-凝胶法制备了CoPt,CoPt-Au纳米颗粒样品. XRD结果说明样品CoPt,CoPt-Au均形成了稳定的面心四方结构L10相CoPt.TEM结果显示，Au元素掺杂促进了CoPt纳米颗粒的尺寸生长.VSM结果表明，Au元素的掺杂增大了CoPt纳米颗粒的矫顽力，对CoPt纳米颗粒磁性的增大有促进作用.

图3　CoPt, CoPt-Au纳米颗粒的磁滞回线图

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(责任编辑:王海波)

The Influence of Au Addition on the Structure and Magnetism of CoPt Nanoparticles

ZHANG Xiao-long，LI Jia,JIANG Yu-hong,LIU Yang,WANG Ya-xin

(CollegeofPhysics,JilinNormalUniversity,Siping，Jilin136000,China)

Abstract:CoPt and CoPt-Au nanoparticles are fabricated by Sol-gel method.Structure,morphology and magnetic properties of CoPt,CoPt-Au were characterized.X-ray diffraction (XRD) results show that CoPt,CoPt-Au were faced centered tetragonal structure(FCT) at 700℃.Transmission electron microscopy (TEM) results indicate that the CoPt-Au nano-particle has the larger size than CoPt.It means that Au could promote the growth of CoPt nanoparticles.The result of vibrating sample magnetometer (VSM) indicates that the pure CoPt nanoparticles has the smaller coercivity than CoPt-Au nanoparticles.It indicates that the addition of Au could improve the magnetism of CoPt nanoparticles.

Key words:CoPt；Au；sol-gel；magnetism；size