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Shengqiang Zhou :Defect induced magnetism in SiC

发布日期:2016-04-25   点击量:

报告题目:

Defect induced magnetism in SiC

报告人:

Shengqiang Zhou

Tenure Junior research leader

邀请人:

谭杨

报告时间:

2016-01-22 09:00

报告地点:

离子束报告厅

报告内容提示:

Defect-induced magnetism is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC sample. In combination with X-ray absorption spectroscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.

For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals.

With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [5]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. We speculate that defect-induced ferromagnetism rather locally appears in particular regions, like surface/interface/grain boundaries.

[1] L. Li, … S. Zhou, Appl. Phys. Lett. 98, 222508 (2011). [2] Y. Wang, … S. Zhou, Phys. Rev. B 90, 214435 (2014). [3] Y. Wang, … S. Zhou, Phys. Rev. B 89, 014417 (2014). [4] Y. Wang, … S. Zhou, Scientific Reports, 5, 8999 (2015). [5] Y. Wang, …, S. Zhou, Phys. Rev. B 92, 174409 (2015).

报告人简介:

德国Dresden-Rossendorf亥姆霍兹研究中心,离子束物理与材料研究所,研究员(PI)

1 M.Ph., 1 Diploma and 2 Ph.D. graduated. 4 Ph.D. ongoing.

150 referred papers, >2400 citations, H-index 26, 7 invited conference talks and 4 invited articles/chapters.

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