No abstract

We study electrical spin injection and detection in n-Ge across Fe3Si/n+-Ge Schottky tunnel barriers. Spin-accumulation signals detected electrically by the three-terminal Hanle-effect measurements have large temperature dependence, and the spin signals disappear at around 200 K. We find that the temperature variation in the spin signals is strongly related to that in the interface resistance of the Fe3Si/n+-Ge contacts. We also observe marked reduction in nonlocal spin-valve signals with increasing temperature in the four-terminal device with almost the same Fe3Si/n+-Ge/n-Ge heterostructure. Note that the nonlocal spin signals depend on not only the measurement temperature but also on the electrical characteristics of the spin injector. Considering the results of three-terminal and four-terminal measurements, we conclude that temperature dependence of the spin signals in our Fe3Si/n+-Ge/n-Ge devices is governed by the electrical characteristics of the spin injector. This study means that it is necessary to consider the effective Schottky-tunnel contacts with the stability on temperature variations for next-generation Ge-based spintronic applications.

To inform room-temperature spin functionality of D03-ordered Fe3Si, we explore tunneling magnetoresistance (TMR) effects in magnetic tunnel junctions (MTJs) consisting of Co60Fe40/AlO x /Fe3Si on Si. We clearly observe reproducible TMR ratios of ∼20% at room temperature for all MTJs fabricated. By using Julliere's formula, the room-temperature spin polarization (P) value for D03-ordered Fe3Si can be roughly estimated to be ranging from 0.18 to 0.45 when we assume the P values from 0.5 to 0.2 for Co60Fe40. This study reveals that the room temperature P value for D03-ordered Fe3Si is relatively small compared with that for Co-based Heusler alloys reported previously.

No abstract

We present two important technologies for silicon-germanium (SiGe) spintronics. First, we show high-quality epitaxial growth of bcc-type ferromagnetic alloys on Si or Ge with atomically controlled interfaces. Second, we establish electrical spin injection and detection across the high-quality interfaces in Si- or Ge-based devices. Combining these technologies with a metal-oxide-semiconductor field-effect transistor structure, we can demonstrate room-temperature detection of spin accumulation and control the magnitude of the spin signals. These novel and interesting results are expected to build the basis of a key technology toward developing next-generation SiGe spintronic devices.