My research: properties of Ga. Mn. As, a magnetic semiconductor Elisa De Ranieri University of Cambridge 2 nd VC, 07 Mar 2007
Semiconductors conduct current only under certain conditions Conduction can be related to the energy of the electrons in the system E Bands of E: conduction and valence band Conduction band empty Valence band full
Semiconductors METALS E gap INSULATORS SEMICONDUCTORS
Ferromagnets Each atom behaves like a small magnet Vector represent the “magnetic moment” Moments couple and align in the same direction even with no applied field Domains are formed energetic reason B Moments align with the external magnetic field
Magnetic semiconductors Semiconducting + magnetic properties density of charge carriers I B V Resistance changes with the magnetic field orientation anisotropic magneto resistance (AMR)
Magnetic semiconductors Gold contacts Channel
Devices… My device fabricated on a Ga. Mn. As 1. Layout designed with Auto. CAD 2. Fabrication 50 m metal evaporation, etching, electron beam lithography 3. Measurements
Clean rooms
Processes
Measurements Cryostat very low temperature Liquid helium inside
Measurements Screen of the parameter analyser
Measurements Data looks like this…
Finally Data needs to be interpreted in view of theoretical knowledge of physics • useful discussion with experts in the field (supervisors, other academics) • publication of results on scientific journals