Carrier and Spin Dynamics in InSb- and InMnSbBased Heterostructures, Giti Khodaparast, Virginia Tech, DMR ,, The samples for this projects are provided by groups of Prof. Furdyna, University of Notre Dame and Prof. Santos, University of Oklahoma.  Recently, there has been much interest in developing and exploring spin based semiconductor devices and phenomena. In the last decade, semiconductor based spintronics has achieved remarkable success following the trend of metal based spintronics such as giant magneto resistance (GMR) effects used in hard disks. Semiconductor spintronics has advantages, over other material systems, in logic, storage, communications, and quantum computation.  The goals of our activities have been to characterize and manipulate spin flip, spin precession, and magnetic ordering in a series of narrow gap semiconductors using several time-resolved magneto-optical techniques. Spin flip Fast Spin precession Long lifetime Magnetic ordering Nonvolatile  As part of our activities, we have shown (K. Nontapot et al., APL, 90, ) that photo-induced carrier density can be used to control the spin relaxation lifetime. Magneto Optical Kerr Effect (MOKE) and Differential Reflectivity (  R/R) are plotted as a function of time for one InMnSb ferromagnetic structure. MOKE signal represents spin relaxation time and  R/R, the photo-induced carrier relaxation time. In the measurements presented in Fig. 1 the photo- induced carrier density is a factor of 100 lower than the experimental data on the same sample presented in Fig. 2. A faster relaxation is observed in the presence of large photo- induced carrier density in Fig. 2 [data is shown for room temperature (RT) and 77 K and for clarity for two different circular polarity of pump beams]. This effect can be important in device applications to alter spin relaxation in situ. Fig. 1 Fig. 2

Giti Khodaparast, Virginia Tech, DMR Group of Prof. Khodaparast at the Physics Department,Virginia Tech. Sponsored by NSF DMR Undergraduate summer research was supported by NSF-REU supplement. Educational activities: One post doctoral associate, two grad-students, three under-grads and a high school student have been involved in different aspects of this project. One of the under-grads, Brett Spencer, has joined the University of Arizona as a grad-student. Dr. Rajeev Kini, a post doctoral associate has taken a position at the National Renewal Energy Laboratory, Golden Colorado. Outreach: Starting lectures on nano-science and nano-technology at the Roanoke Governor’s school this fall. Students from several remote districts attend this school to take their math and science classes. In concert with these lectures, internet-based tutorials will be developed that can be accessed not only by high school students but also by learners and educators who do not have access to the traditional university system. One high school student, Ashley Aissis, is setting up a photoluminescence measurement.