The 367th forum: Novel Magnetic Effects in Ferromagnetic Semiconductor Films with Graded Composition
Marquez Endowed Chair of Physics, University of Notre Dame
Professor Furdyna obtained his B.S degree in physics from Loyola University, Chicago, in 1955; and his Ph.D. in experimental solid state physics from Northwestern University in 1960. After two postdoctoral years in Northwestern's Department of Electrical Engineering (1960-62), he joined the M.I.T. Francis Bitter National Magnet Laboratory in 1962. In 1966 he joined the Physics Department at Purdue University as Associate Professor, and was promoted to Professor in 1972. At Purdue he served as Director of the Materials Research Laboratory from 1982 to 1985. In 1987 he was appointed to the Marquez Endowed Chair of Physics at the University of Notre Dame. His current research interests include materials preparation of magnetic and semiconductor nanostructures by molecular beam epitaxy; and structural, magnetic and magnetotransport measurements of nanoscale systems. During his professional career Prof. Furdyna has been Ph.D. advisor to 32 graduate students, and sponsored 16 post-doctoral scholars. He is the author or co-author of 850 publications in the area of materials science, with a focus on semiconductor physics and magnetics, with over 20,000 citations. For his scientific accomplishments he was awarded honorary doctorates by Warsaw University in October 2002, and by Purdue University in May 2007. In 2009 he was awarded the Nicolaus Copernicus Medal by the Polish Academy of Sciences. Prof. Furdyna is Fellow of the American Physical Society and of the American Association for the Advancement of Science.
In this presentation I will discuss the effects of compositional grading of the quaternary alloy Ga1-xMnxAs1-yPy on its ferromagnetic properties. The compositional grading is obtained by sequentially increasing the phosphorus content in Ga1-xMnxAs1-yPy as the film is grown by molecular beam epitaxy. Note that in a uniform Ga1-xMnxAs1-yPy film the presence of P leads to three important consequences. First, it affects the exchange interaction between Mn ions, and thus the Curie temperature of the material. Second, the presence of P automatically affects the strain within the film, which in turn affects its magnetic anisotropy. And, finally, grading the P content in a Ga1-xMnxAs1-yPy film will result in a gradient of the concentration of holes that mediate the Mn-Mn exchange. Importantly, this automatically leads to removal of inversion symmetry between successive atomic layers along the gradient. One thus expects that the properties arising from graded strain and composition will result in entirely new magnetic properties, with novel functionalities. I will present magneto-transport and magnetization studies of such graded structures, which reveal that applying a strong magnetic field to such graded structure “imprints” an internal magnetic field onto the system, thus changing its the magnetic anisotropy in a programmable way. Such ability to permanently manipulate magnetic anisotropy of a ferromagnetic semiconductor holds out the possibility of novel magnetic memory applications.
Collaborators: Margaret Dobrowolska, Xinyu Liu, Sining Dong, Sangoon Lee, Seul-Ki Bac, Yonglei Wang, Sergei Rouvimov, and Vitalii Vlasko-Vlasov
邀 请 人：靳常青（电话：8264 9163）
联 系 人：李园园（电话：8264 9364）