物理化学学报 >> 2018, Vol. 34 >> Issue (4): 437-444.doi: 10.3866/PKU.WHXB201709043

论文 上一篇    

点缺陷引起中子辐照MgO(110)单晶的铁磁性

曹梦雄1,王兴宇1,马亚茹1,马春林1,周卫平1,*(),王晓雄1,王海欧2,谭伟石1,3,*()   

  1. 1 南京理工大学理学院应用物理系，软化学与功能材料教育部重点实验室，南京210094
    2 杭州电子科技大学材料物理研究所，杭州310018
    3 湖南城市学院信息与电子工程学院，湖南益阳413002
  • 收稿日期:2017-08-18 发布日期:2018-01-02
  • 通讯作者: 周卫平,谭伟石 E-mail:wpzhou@njust.edu.cn;tanweishi@njust.edu.cn
  • 基金资助:
    国家自然科学基金(U1332106);国家自然科学基金(11604147);国家自然科学基金(11604067);江苏省普通高校研究生科研创新项目(CXLX13_179)

Point Defects Induced Ferromagnetism in Neutron Irradiated MgO(110) Single Crystals

Mengxiong CAO1,Xingyu WANG1,Yaru MA1,Chunlin MA1,Weiping ZHOU1,*(),Xiaoxiong WANG1,Haiou WANG2,Weishi TAN1,3,*()   

  1. 1 Key Laboratory of Soft Chemistry and Functional Materials of Ministry of Education, Department of Applied Physics, School of Science, Nanjing University of Science and Technology, Nanjing 210094, P. R. China
    2 Institute of Materials Physics, Hangzhou Dianzi University, Hangzhou 310018, P. R. China
    3 College of Communication and Electronic Engineering, Hunan City University, Yiyang 413002, Hunan Province, P. R. China
  • Received:2017-08-18 Published:2018-01-02
  • Contact: Weiping ZHOU,Weishi TAN E-mail:wpzhou@njust.edu.cn;tanweishi@njust.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(U1332106);the National Natural Science Foundation of China(11604147);the National Natural Science Foundation of China(11604067);Scientific Research Innovation Projects of Jiangsu Province for University Graduate Students, China(CXLX13_179)

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摘要：

对MgO(110)单晶进行中子辐照，辐照剂量从1.0 × 1016到1.0 × 1020 cm-2。基于黄昆漫散射理论，我们计算了MgO晶体中的立方缺陷和偶极力缺陷引起的X射线漫散射强度分布图。通过X射线漫散射及紫外-可见光(UV-Vis)吸收光谱实验表征了晶体的点缺陷组态，并利用超导量子干涉仪(SQUID)测量了样品的磁性。ω–2θ和摇摆曲线说明MgO单晶经中子辐照后产生了晶格畸变，晶体中存在一定浓度的点缺陷。倒易空间图(RSM)显示中子辐照的MgO单晶存在漫散射现象。与计算得到的漫散射分布图对比分析可知，中子辐照的MgO(110)单晶中产生了弗仑克尔缺陷。UV-Vis吸收光谱表明所有辐照晶体中存在阴离子单空位缺陷。辐照剂量较高(1.0 × 1019和1.0 × 1020 cm-2)的样品中存在O空位的聚集。磁性测量显示中子辐照后的MgO(110)单晶在室温下依然是抗磁性，但在低温下具有铁磁性，最大饱和磁化强度达到0.058 emu·g-1。通过中子辐照的方法，可以使MgO(110)单晶产生点缺陷引起的低温铁磁性。利用F色心交换机制可以解释中子辐照MgO晶体中的O空位缺陷与铁磁性之间的关系。

关键词: MgO单晶, 中子辐照, 点缺陷, d0铁磁性, RSM, 色心

Abstract:

The MgO(110) single crystals were neutron-irradiated with different doses ranging from 1.0×1016 to 1.0×1020 cm-2. The isointensity profiles of the X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were calculated on the basis of the Huang scattering theory. The X-ray diffuse scattering and the UV-Vis absorption spectra were recorded to investigate the point defect configurations in the MgO(110) crystals. Furthermore, the magnetic properties were characterized by a superconducting quantum interference device magnetometer. The ω–2θ curves and rocking curves implied that neutron irradiation enhanced the lattice distortion. The point defects were produced in irradiated MgO crystals. The measured reciprocal space mappings (RSMs) revealed that the notable diffuse scattering was presented in irradiated MgO. Compared with the calculated diffuse scattering intensity profile, it was evident that Frenkel defects were introduced in the irradiated samples. The UV-Vis spectra indicated that anion O vacancy defects had been introduced in irradiated MgO. The single vacancies could be aggregated in irradiated samples with higher doses (1.0×1019 and 1.0×1020 cm-2). Although the irradiated MgO(110) single crystals were diamagnetic at room temperature, they became ferromagnetic at low temperature. The maximum saturation magnetization was found to be 0.058 emu·g-1. By means of neutron irradiation, defect-mediated ferromagnetism could be achieved at low temperature. The correlation between ferromagnetism and O vacancies in neutron-irradiated MgO could be described using F-center exchange mechanism.

Key words: MgO single crystal, Neutron irradiation, Point defect, d0 ferromagnetism, RSM, Color center