Comparison of Spin Signals Between 3T Hanle and 4T Non-Local Methods for Co2Fe(Al,Si)/n-GaAs Junctions

We investigated spin signals for Co₂Fe(Al,Si)/n-GaAs Shottoky tunnel junctions by three terminal (3T) Hanle and four terminal (4T) non-local measurements. The ordering structure and magnetic moment increased with T_CFAS up to 300 °C. The spin signals for Co₂Fe(Al,Si)/n-GaAs Shottky tunnel junctions were clearly observed and these were also affected by T_CFAS, however, the T_CFAS dependency was different obtained from 3T Hanle and 4T non-local measurements. The spin signals in 3T Hanle measurement decreases with increasing T_CFAS up to 300 °C and increase for the sample with T_CFAS = 400 °C. On the other hand, the spin signals in 4T non-local measurement increases with T_CFAS up to 300 °C and decreases for the sample with T_CFAS = 400 °C. This result obtained from 4T non-local measurement could be explained by the spin polarization of Co₂Fe(Al,Si), and that from 3T Hanle measurement would not come from the spin polarization of Co₂Fe(Al,Si) but other source, such as localized state around the interface between Co₂Fe(Al,Si) and n-GaAs.