<strong>Nd</strong>含量对磁控溅射<strong>Si(111)/Cr/Nd-Co/Cr</strong>薄膜结构与磁性的影响

doi:10.11900/0412.1961.2018.00490

金属学报

2019, Vol. 55

Issue (10): 1349-1358 DOI: 10.11900/0412.1961.2018.00490

本期目录 | 过刊浏览

Nd含量对磁控溅射Si(111)/Cr/Nd-Co/Cr薄膜结构与磁性的影响

何贤美¹,童六牛²(

),高成²,王毅超²

1. 安徽工业大学数理科学与工程学院马鞍山 243002
2. 安徽工业大学材料科学与工程学院马鞍山 243002

Effect of Nd Content on the Structure and Magnetic Properties of Si(111)/Cr/Nd-Co/Cr Thin Films Prepared by Magnetron Sputtering

HE Xianmei¹,TONG Liuniu²(

),GAO Cheng²,WANG Yichao²

1. School of Mathematics and Physics, Anhui University of Technology, Ma'anshan 243002, China
2. School of Materials Science and Engineering, Anhui University of Technology, Ma'anshan 243002, China

引用本文:

何贤美, 童六牛, 高成, 王毅超. Nd含量对磁控溅射Si(111)/Cr/Nd-Co/Cr薄膜结构与磁性的影响[J]. 金属学报, 2019, 55(10): 1349-1358.
Xianmei HE, Liuniu TONG, Cheng GAO, Yichao WANG. Effect of Nd Content on the Structure and Magnetic Properties of Si(111)/Cr/Nd-Co/Cr Thin Films Prepared by Magnetron Sputtering[J]. Acta Metall Sin, 2019, 55(10): 1349-1358.

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摘要:

采用磁控溅射技术制备了系列Si(111)/Cr(10 nm)/NdCo_x(400 nm)/Cr(10 nm)薄膜，其中，Co/Nd原子比x=2.5~7.2。利用XRD、SEM、AFM/MFM、VSM等手段研究了Nd含量对制备态薄膜垂直磁各向异性(PMA)与磁畴结构及退火态薄膜相结构与磁性的影响规律。结果表明，随着Nd含量的变化，制备态Nd-Co薄膜的垂直磁各向异性能K_u在x=5.2附近存在一个较宽的峰，峰值处K_u=(80±5) kJ/m³。MFM图像的相移均方根偏差(Δ?_rms)在临界成分x=5.2处也存在最大值，其成分依赖关系与K_u-x的变化趋势一致。薄膜应力诱导的磁弹各向异性是导致溅射Nd-Co非晶薄膜PMA的主要原因。经过在600 ℃真空快速退火后，所有薄膜均析出了Nd₂Co₁₇、NdCo₂、Nd₄Co₃等金属间化合物，而NdCo_5±_x相纳米晶只在Nd过量(至少4%，原子分数)的x=2.5和3.8薄膜中才被观测到，同时还伴随着Nd₂Co₇共生相的析出。室温磁性测试结果表明，NdCo_5±_x和Nd₂Co₇相纳米晶的析出，导致x=2.5和3.8薄膜面内矫顽力(分别为H_c-in=54和51 kA/m)显著增强；而x≥4.4样品的面内矫顽力保持在低值(H_c-in=4~8 kA/m)范围内。

关键词 ：磁性薄膜, 垂直磁各向异性, 稀土-过渡族金属合金, NdCo₅金属间化合物, 条纹磁畴

Abstract：

A series of Si(111)/Cr(10 nm)/NdCo_x(400 nm)/Cr(10 nm) thin films with the atomic ratio of Co/Nd (x) varying from 2.5 to 7.2 were prepared by radio frequency magnetron sputtering. The influence of Nd content on the structure and magnetic properties of the as-prepared and post annealed films were investigated by XRD, SEM, VSM and AFM/MFM. Magnetic measurements at room temperature show that the compositional variation of the perpendicular anisotropy energy (K_u) exhibits a broad peak around x=5.2 with maximum of K_u=(80±5) kJ/m³ for the as-prepared Nd-Co amorphous films. MFM characterization shows that the root mean square deviation of phase shift in MFM images (Δ?_rms) also have a compositional dependence which is similar to that of K_u-x. The experimental results show that the stress induced magneto-elastic anisotropy is the primary origin of the perpendicular magnetic anisotropy (PMA) in the as-prepared Nd-Co amorphous film. After rapid thermal annealing (RTA) process in a vacuum atmosphere at 600 °C, intermetallic compounds such as Nd₂Co₁₇, Nd₄Co₃ and NdCo₂ are precipitated in all the studdied films, while NdCo_5±_x nanocrystals accompanied by the precipitation of Nd₂Co₇ symbiotic phase were observed only in the films with x=2.5 and 3.8 (the atomic fraction of Nd excesses at least 4%). The in-plane coercivity of the films with x=2.5 and 3.8 was significantly enhanced (H_c-in=54, 51 kA/m) due to the precipitation of NdCo_5±_x and Nd₂Co₇ nanocrystals, while that of the samples with x>4.4 remained low value (H_c-in=4~8 kA/m).

Key words： magnetic thin film perpendicular magnetic anisotropy rare-earth-transition-metal alloy NdCo₅ intermetallic compound striped magnetic domain

收稿日期: 2018-10-30

ZTFLH:

TM271

基金资助:国家自然科学基金项目(51671001)

作者简介: 何贤美，女，1963年生，副教授

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https://www.ams.org.cn/CN/10.11900/0412.1961.2018.00490 或 https://www.ams.org.cn/CN/Y2019/V55/I10/1349

图1 制备态Si(111)/Cr(10 nm)/NdCox (400 nm)/Cr(10 nm)薄膜的XRD谱

图2 制备态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的面内与法向磁滞回线

图3 制备态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的饱和磁化强度(Ms)和平面内饱和磁化场(Hs-in)，及有效磁各向异性能(Keff)、形状各向异性能(Kd)和磁弹性各向异性能(Kme)随x的变化

图4 制备态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的MFM像

图5 制备态薄膜的单轴磁各向异性常数(Ku)和MFM像相移的均方根偏差(Δ?rms)随x的变化曲线

图6 制备态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的MFM和AFM像

图7 制备态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm) 薄膜中Co和Nd元素的二维成分分布图

图8 制备态Si(111)/Cr(10 nm)/NdCo5.2 (400 nm)/Cr(10 nm)薄膜分别经过在不同退火温度(Ta)真空退火后的面内磁滞回线，及面内矫顽力(Hc-in)和剩磁比(Mr/Ms)随Ta的变化关系

图9 在600 ℃快速退火30 min后Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的XRD谱

图10 经600 ℃快速退火30 min后Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的室温磁滞回线

图11 室温下测定的退火态Si(111)/Cr(10 nm)/NdCox(400 nm)/Cr(10 nm)薄膜的Hc-in随x的变化关系

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