Measurement of Oblique Hanle Effect in {100} Fe Spin LEDs

In previous oblique Hanle work (1) on CoFe spin LEDs a prefactor equal to T$_{S}$/$\tau $ remained undetermined. Here $\tau $ and T$_{S}$ are the electron lifetime and spin lifetime, respectively. We have removed this uncertainty by carrying out a combined Hanle and magneto-EL study in the Faraday geometry of surface emitting [100] Fe spin LEDs. These experiments yield the values for $\tau $ and T$_{S }$ from which we can extract the spin relaxation time $\tau _{S}$. These parameters were determined in the 5-120 K temperature range. A parallel experiment on [110] Fe spin LEDs gave a null result even though these devices show comparable polarization in the Faraday geometry. This result is attributed to the short spin lifetime of spin oriented perpendicular to the [110] axis (2). This work was supported by the DARPA SpinS program, ONR, and NSF. 1. Motsnyi et. al. Appl. Phys. Lett. \underline {81}, 265, (2002). 2. D\"{o}hrmann et. al., Phys. Rev. Lett. \underline {93}, 147405-1, (2004).