Singh Abhinav Pratap, Kumar Ravi, Thakur P, Brookes N B, Chae K H, Choi W K
Materials Science Division, Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India.
J Phys Condens Matter. 2009 May 6;21(18):185005. doi: 10.1088/0953-8984/21/18/185005. Epub 2009 Mar 11.
A study of the electronic structure and magnetic properties of Co doped ZnO thin films synthesized by ion implantation followed by swift heavy ion irradiation is presented using near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. The spectral features of NEXAFS at the Co L(3,2)-edge show entirely different features than that of metallic Co clusters and other Co oxide phases. The atomic multiplet calculations are performed to determine the valence state, symmetry and the crystal field splitting, which show that in the present system Co is in the 2+ state and substituted at the Zn site in tetrahedral symmetry with 10Dq = -0.6 eV. The ferromagnetic character of these materials is confirmed through XMCD spectra. To rule out the possibilities of defect induced magnetism, the results are compared with Ar annealed and Ar-ion implanted pure ZnO thin films. The presented results confirm the substitution of Co at the Zn site in the ZnO matrix, which is responsible for room temperature ferromagnetism.
本文通过近边X射线吸收精细结构（NEXAFS）和X射线磁圆二色性（XMCD）测量，对离子注入后再经快速重离子辐照合成的Co掺杂ZnO薄膜的电子结构和磁性进行了研究。Co L(3,2)边的NEXAFS光谱特征与金属Co团簇和其他Co氧化物相的光谱特征完全不同。进行了原子多重态计算以确定价态、对称性和晶体场分裂，结果表明在本体系中Co处于2+态，以四面体对称取代Zn位点，10Dq = -0.6 eV。通过XMCD光谱证实了这些材料的铁磁特性。为排除缺陷诱导磁性的可能性，将结果与Ar退火和Ar离子注入的纯ZnO薄膜进行了比较。本文结果证实了Co在ZnO基体中取代Zn位点，这是室温铁磁性的原因。
