Au摻雜對CoPt納米顆粒結(jié)構(gòu)和磁性的影響

張小龍，李佳， 姜雨虹，劉洋，王雅新*

(吉林師范大學(xué) 物理學(xué)院，吉林 四平 136000)

摘要:利用溶膠-凝膠法制備CoPt, CoPt-Au納米顆粒.并對制備的樣品(CoPt, CoPt-Au納米顆粒)的結(jié)構(gòu)、形貌以及磁學(xué)性能進行了表征.X 射線衍射(XRD)結(jié)果表明，700°C時，CoPt, CoPt-Au納米顆粒均為面心四方結(jié)構(gòu)(FCT)的L10相.透射電子顯微鏡(TEM)結(jié)果表明，CoPt較CoPt-Au的顆粒尺寸小，說明了Au摻雜可能促進了CoPt納米顆粒的尺寸生長.振動樣品磁強計(VSM)結(jié)果顯示，CoPt-Au較CoPt的矯頑力大，說明一定量的Au元素摻雜可以促進CoPt納米顆粒磁性的增長.

關(guān)鍵詞:CoPt; Au; 溶膠-凝膠; 磁性; 尺寸

DOI:10.13877/j.cnki.cn22-1284.2015.10.014

收稿日期：2015-07-29

基金項目：國家自然科學(xué)

作者簡介：張小龍，男，吉林四平人，助理實驗師，碩士.

通訊作者：王雅新，女，吉林四平人，教授，博士，碩士生導(dǎo)師.

中圖分類號：0482.54文獻標志碼：A

CoPt(FePt)磁性納米材料在藥物靶向治療，磁存儲等多個領(lǐng)域具有潛在的應(yīng)用價值[1-9].其中，CoPt納米材料以其較好的熱穩(wěn)定性、抗氧化性和抗腐蝕性等優(yōu)點而備受青睞[10，11].當CoPt磁性納米材料的化學(xué)成分不同時，其具有不同的結(jié)構(gòu)相，例如：面心四方結(jié)構(gòu)(FCT)的L10相, L11相, L12相, 面心立方結(jié)構(gòu)(FCC)相，且具有不同結(jié)構(gòu)相的CoPt納米材料在不同領(lǐng)域均有應(yīng)用[12，13].早期制備的CoPt納米材料磁性較小，且制備方法復(fù)雜，有毒，已經(jīng)不能滿足現(xiàn)階段磁存儲對于存儲介質(zhì)的需求[14-21].為了滿足磁存儲的需求，進一步提高CoPt納米材料的磁性，以及限制其顆粒尺寸的增長，部分研究學(xué)者在制備CoPt納米材料過程中添加其它元素，例如C, Ag, Cu, Si等[21-25].本文主要是利用溶膠-凝膠法合成CoPt, CoPt-Au納米顆粒，利用XRD，TEM，VSM等測試手段對樣品進行了系統(tǒng)的結(jié)構(gòu)與性能表征.

1實驗

實驗原料：六水合氯鉑酸(H2PtCl6·6H2O),六水合硝酸鈷(Co(NO3)2· 6H2O),一水合檸檬酸(C6H8O7·H2O)以及四氯金酸(HAuCl4)等試劑.實驗具體步驟為：按照一定的摩爾比例稱取試劑，將試劑混合攪拌一段時間，得到混合液，混合液經(jīng)過攪拌，干燥，最后在氬氣氣氛下進行熱處理1小時，即可制備出有序的L10相CoPt納米顆粒.

2結(jié)果與討論

圖1為樣品的XRD圖譜.圖1可以看出樣品CoPt, CoPt-Au納米顆粒均形成(001)，(110),(111),(200),(002),(201),(112),(220)以及(202)晶格峰,不含有其它的雜質(zhì)峰，說明樣品CoPt,CoPt-Au形成了純相的面心四方結(jié)構(gòu)CoPt納米顆粒.樣品CoPt-Au的XRD圖譜中，存在Au的(111),(200),(220)衍射峰，說明樣品CoPt-Au中含有Au單質(zhì).為了進一步驗證Au摻雜對樣品的影響，我們利用公式S=[1-(c/a)]/[1-(c/a)th][26](S為樣品的有序度，(c/a)為樣品的實驗值(c/a)th為樣品的理論值，其中a,c為樣品的晶格參數(shù))對樣品的有序度進行分析，分析結(jié)果顯示，樣品CoPt和CoPt-Au的有序度分別為0.94和0.96,這一結(jié)果說明Au元素摻雜提高了CoPt納米顆粒的有序度.我們利用謝樂公式：L=0.89λ/βcosθ(L,λ，β，θ分別為樣品的尺寸，X射線的入射波長為0.15406nm，布拉格衍射角，衍射峰的半高寬)對樣品CoPt,CoPt-Au納米顆粒進行了尺寸分析，樣品CoPt、CoPt-Au的平均顆粒尺寸分別為16nm、20nm左右.謝樂公式結(jié)果表明，Au元素摻雜促進了CoPt納米顆粒的尺寸增長.

圖1　CoPt,CoPt-Au納米顆粒的XRD圖譜

圖2為樣品CoPt(a), CoPt-Au(b)納米顆粒的TEM形貌圖.TEM結(jié)果顯示，樣品CoPt, CoPt-Au均呈現(xiàn)橢球形，樣品CoPt-Au較CoPt團聚現(xiàn)象明顯.此外，樣品CoPt-Au的顆粒平均尺寸大于CoPt的顆粒尺寸，這一結(jié)果與Nandwana等人研究的結(jié)果相似[27],同時與XRD結(jié)果相對應(yīng).

圖2　CoPt, CoPt-Au納米顆粒的TEM圖

圖3為樣品CoPt, CoPt-Au納米顆粒的磁滯回線圖.從圖3可以看出，各樣品的矯頑力大小依次為4970 Oe、6410 Oe，這說明Au元素的摻雜能夠提高CoPt納米顆粒的矯頑力，且樣品CoPt-Au的飽和磁化強度(Ms)較樣品CoPt的飽和磁化強度(Ms)小，參照XRD結(jié)果表明，這可能由樣品CoPt-Au的有序度較樣品CoPt的有序度大引起的.

3結(jié)論

本文利用改進的溶膠-凝膠法制備了CoPt,CoPt-Au納米顆粒樣品. XRD結(jié)果說明樣品CoPt,CoPt-Au均形成了穩(wěn)定的面心四方結(jié)構(gòu)L10相CoPt.TEM結(jié)果顯示，Au元素摻雜促進了CoPt納米顆粒的尺寸生長.VSM結(jié)果表明，Au元素的摻雜增大了CoPt納米顆粒的矯頑力，對CoPt納米顆粒磁性的增大有促進作用.

圖3　CoPt, CoPt-Au納米顆粒的磁滯回線圖

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(責任編輯: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