摘要
采用射频(RF)磁控溅射方法,在2种基底温度(TS=25,310℃)的基片上制备了结构为Si(111)/NdFeCo(610 nm)/Cr(10 nm)的薄膜样品,溅射氩气压保持在pAr=0.1 Pa。采用X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)、振动样品磁强计(VSM)、原子力显微镜(AFM)和磁力显微镜(MFM)等实验技术,研究了一步和三步快速退火(RTA-I和RTA-II)工艺对两种薄膜微结构和磁性的影响。结果显示,室温基底上沉积的样品呈非晶态,磁畴为面内磁畴结构;而加热基底上制备的样品则析出了Nd2Fe17和Nd6Fe13Si纳米晶,垂直磁各向异性(PMA)反常增强,垂直磁各向异性能为K⊥=1.18×105J·m-3,磁畴为平行条纹畴。在TA=500℃经过RTA-I/-II工艺后,基底加热样品析出的Nd2Fe17和Nd6Fe13Si纳米晶继续长大,磁畴由条纹畴转变为磁斑畴。而室温基底上制备的薄膜经RTA-I/-II退火后则没有观察到界面硅化物,却发现结晶出的Fe Co和Nd2Fe15Co2纳米晶粒大小和取向敏感地依赖于退火工艺。即一步快速退火工艺有利于析出(111)织构的Nd2Fe15Co2纳米晶,而三步快速退火工艺则易于诱导出(200)织构的Fe Co纳米晶。实验结果表明,基底加热薄膜中析出的Nd2Fe17纳米晶与Nd6Fe13Si界面硅化物的热膨胀特性正好相反,由此产生的残余内应力与磁弹各向异性,是导致基底加热薄膜PMA反常增强的主要原因。
Two kinds of Si （111 ）/NdFeCo（610 nm）/Cr（ 10 nm） thin film samples were prepared by radio frequency （RF） magne- tron sputtering under working Ar pressure （PAr） of 0. 1 Pa at substrate temperature （ Ts ） of 25 and 310 ℃, respectively. The effects of one-step and three-step rapid thermal annealing （RTA） processes （denoted as RTA-I and RTA-II, respectively） on crystal structures and magnetic properties of the films were characterized by X-ray diffraction （XRD）, field emission scanning electron microscope （FE- SEM）, vibrating sample magnetometer （ VSM ）, atomic force microscope （ AFM ）, and magnetic force microscopy （ MFM ） , respec- tively. It showed that the film deposited at room temperature （RT） was in amorphous state with an in-plane dominated magnetic anisot- ropy, while the film deposited at Ts = 310 ℃ exhibited a strong perpendicular magnetic anisotropy （PMA） with a parallel stripe domain structure. The perpendicular anisotropy energy was determined to be K, = 1.18 x 105 J .m-3. The XRD pattern suggested that the Nd2Fel7 nanocrystals and Nd6Fe13Si silicides in nano-size appeared in the film deposited at Ts = 310 ℃. After processed at TA = 500 ℃ by RTA-I and RTA-II processes, respectively）, the grains of Nd2 Felt and Nd6Fe13 Si nanocrystals in the films deposited at Ts = 310 ℃ continued to grow up, the stripe domains in virgin state transformed into magnetic spot domains. However, the interfaciaI silieides of the Nd6 Fe13 Si crystallites were not observed in the films deposited at RT and subsequently processed by RTA-I and RTA-II processes, respectively. Instead, it was shown that the crystal orientation and grain size of FeCo and Nd2Fe15Co2 nanocrystals are senstive to the annealing processes of RTA-I and RTA-II, respectively. In other words, one-step RTA process made the RT-deposited film crystallize into Nd2 Fe15 C02 dominated crystallites with （ 111 ） texture, while a three-step RTA process resulted in the crystallization of FeCo n
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2015年第4期322-330,共9页
Chinese Journal of Rare Metals
基金
安徽省教育厅重点项目(KJ2011A052)
国家教育部归国留学人员科研启动基金项目(011102)资助
