Room temperature ferromagnetism in semiconducting oxides – Chandran Sudakar

Date: Mon. November 10th, 2008, 12:30 pm-1:30 pm
Location: Rockefeller 221

Diluted magnetic semiconductors are formed when magnetic transition metal ions are doped in small concentrations into a semiconductor host lattice. The first reports of ferromagnetism being observed at room temperature in a dilutely doped semiconducting oxide film attracted a great deal of attention, but were also met with considerable skepticism. These materials would have enormous potential for developing new classes of electronic devices, but there were concerns that the observed magnetism arose from impurity contributions, rather than any intrinsic property of the material. Although there has been some progress made in understanding these systems, in particular, the important role played by oxygen vacancies, there is still vigorous debate surrounding the fundamental origin of the magnetic signal in these oxides. I will present some of the experimental results where nanoscale clusters, surface defects and oxygen vacancies play significant role in determining the magnetism in these materials. I will also present some results demonstrating that ferromagnetism can arise in semiconducting oxides even in the absence of magnetic dopants. Finally, I will conclude with some very recent measurements establishing that the ferromagnetic order in In2O3 is associated with a finite spin polarization and discuss the implications of this result.