Room Temperature sp-d exchange in InMnAs films

1. Northwestern University Room Temperature sp-d exchange in InMnAs films DMR 0511523 Bruce Wessels I. Intellectual Merit: • In contrast to earlier MBE work,[1] InMnAs is a room temperature ferromagnetic semiconductor with a Tcof 330 K. • Ferromagnetic interactions are not well understood in these materials. • Use polar magnetic circular dichroism (MCD) spectroscopy to determine the nature of the interactions. • A well resolved MCD peak at 2.62 eV is observed at room temperature. • Peak corresponds to exchange splitting of the valence and conduction bands. • Exchange splitting implies that there are spin polarized holes in the valence band at room temperature. Fig. 1:MCD spectrum of In0.98Mn0.02As at T=298K. Fig. 2: Schematic of the interaction between Mn dimers and itinerant holes. [1] Schallenberg, Appl. Phys. Lett. 89 042507 (2006)

2. Northwestern University Normal Currents Room Temperature sp-d exchange in InMnAs films DMR 0511523 Bruce Wessels II. Broader Impacts: • Spin polarized currents will allow for a new generation of spintronic devices including the spin bipolar junction transistor, and spin light emitting diodes. • Spintonic devices would be nonvolatile, more power and space efficient, and faster as compared with charged semiconductor based devices.[1] • Practical spintronic devices must have spin polarized carriers at room temperature. • MCD of InMnAs provides evidence of room temperature spin polarized holes. • Adam Kueltzo a member of the REST program, assisted in the spectroscopic measurements. Spintronic Device Currents Ferromagnet Fig. 3: Currents in charged based devices versus spin polarized currents in spintronic devices. Ferromagnet acts as a spin filter. Ti/Au n-InAs Ti/Au p-InMnAs n-InAs Fig. 4: Proposed spin bipolar junction transistor with InMnAs as the active ferromagnetic layer. [1] S.A Wolf et. al, Science 294, 1488 (2001)