P12

Preparation of magnetic tunnel junctions with ferromagnetic materials of high spin polarization (Ando)

The key goal of our project is to demonstrate spin polarization in devices such as magnetic tunnel junctions (MTJs) with half-metallic material electrodes. Some Heusler alloys have been theoretically predicted to have high spin polarization, and some have been proven experimentally. In the MTJ structure, however, there are many problems with maintaining the high spin polarization at the interface between the ferromagnetic electrode and an insulator.

To overcome these problems, this project will focus on the preparation of high quality single crystal half-metallic electrodes and the control of the site ordering of the alloys by the introduction of appropriate post preparation annealing processes. Investigations of Co₂MnSi_1-xAl_x and Co₂MnGe are planned. To control the interface structures of the MTJs with the half-metallic electrodes, both the material and preparation conditions for the barriers will also be investigated.

To evaluate the quality of the single crystal films and the interfaces of the MTJs, the magnetic anisotropy and the damping constants will be measured using the ferromagnetic resonance technique. The spin polarization at the interface of the MTJs should be measured electrically. For this reason, the tunnel spectroscopy technique will be used in parallel with the tunneling magnetoresistance (TMR) measurements.