Making Semiconductors Ferromagnetic: Opportunities and Challenges

Presented by J. K. Furdyna, Department of Physics, University of Notre Dame

Introducing ferromagnetism into semiconductors holds out the promise of using the spin of the electron, alongside its charge, for the purpose of increasing the functionality of semiconductor devices. This is the focus of the emerging technology referred to as "spintronics". It has already been demonstrated that III-V semiconductor compounds (e.g., GaAs) can indeed be made ferromagnetic by replacing a fraction of the III-V lattice by substitutional Mn ions to form III{1-x}Mn{x}V alloys (e.g., Ga{1-x}Mn{x}As). The Mn enters the III-V lattice as divalent Mn++ ions, and thus act both as magnetic moments and as acceptors. It is the large concentration of holes generated by the acceptor nature of Mn++ which provides the mechanism for long-range ferromagnetic coupling between the Mn spins. In this talk I will discuss the various methods of preparing such III{1-x}Mn{x}V alloys; their representative ferromagnetic properties (the Curie temperature, magnetic domains, magnetic anisotropy, etc.) methods of controlling these properties; and I will present several examples of prototype spintronic devices based on these materials. And I will give special emphasis to the challenges that still remain to be overcome in order to bring these applications to practical reality.