Date: 2024-02-01
Time: 10:00
Venue: M234
Speaker: Professor J. M. D. Coey
               Trinity College Dublin

报告摘要:

Ferrimagnets, especially those that exhibit compensation, have special advantages as spintronic materials. Important families are manganese-based metallic compounds and crystalline or amorphous compounds of iron or cobalt with a heavy rare earth. They exhibit large coercivity when the moment disappears at Tcomp, ultra-fast spin dynamics and single-pulse all-optical switching. Interstitial face centred-cubic Mn₄N is a noncollinear triangular ferrimagnet where compensation is achieved at room temperature by replacing some Mn on cube corner sites by non-magnetic Ga in the metallic ‘antiperovskite’ Mn_4-xGa_xNat_x=0.17in thin films, which are tetragonal with perpendicular anisotropy, and at x=0.26 in the bulk. Mn₄N shows signs of a topological Hall effect associated with its non-collinear spin structure. Large50μm — I mm domains have been imaged by MOKE and MFM, but spectroscopic MOKE shows little domain contrast in the red. Single-pulse all-optical switching is observed in the Mn Heusler ferrimagnet Mn₂Ru_xGa, but not Mn_4-xGa_xN. Potential applications will be reviewed.

报告人简介：

Michael Coey is a Professor of Physics at Trinity College Dublin. He has studied many aspects of magnetism and magnetic materials, and published numerous papers and several books, two of which have been translated into Chinese (Magnetic Glasses in 1990 and Magnetism and Magnetic Materials in 2024). His main contributions have been in amorphous magnetic materials, magnetic minerals, rare-earth permanent magnets, dilute and disordered magnetic oxides, magnetoelectrochemistry, and spin electronics. He received his PhD from the University of Manitoba in 1971, and worked for seven years at the CNRS in Grenoble, before moving to Ireland. He has spent extended periods at Universities and Institutes including UC San Diego, IBM, Strasbourg, NU Singapore, Beihang and the IOP, where he gave a course of lectures on Mossbauer Spectroscopy in 1980. He is a Fellow of the Royal Society, an overseas member of the National Academy of Science of the USA and recipient of the Gold Medal of the Royal Irish Academy.

联系人: 胡江平 研究员（8264 9818）

            韩秀峰 研究员（8264 9268）