Diffusion of spins in a strongly spatially varying local magnetic field

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In recent years, the field of spintronics has gained immense interest in the research community. In conventional computing, data is encoded by turning electrical signals on and off; with spintronics, data is encoded with electron spin, allowing for new electronic devices that can move more data at reduced voltages. To further this field, an understanding of spin behavior at the local level is necessary. In my group, magnetic force detection experiments are being used to understand these local phenomena. In these experiments, a micro-magnetic probe couples to the spins generated in a gallium arsenide sample. The sample in these experiments is a 2 micron thick n-GaAs (3e16 cm-3 Si doped) epitaxial membrane. Spins were injected into the membrane over a 10 micron region using standard optical pumping techniques. My presentation focuses on numerical analysis of the spin diffusion equation to better understand the effects of the local magnetic field generated by the probe tip. These simulations provide spatial maps of spin polarization. They also provide information concerning the procession of the spins about an external transverse magnetic field. These were simulated for the conditions experienced by the sample in the experiment. A key result is that the presence of localized, strongly inhomogeneous magnetic fields leads to spatial features in the spin distribution smaller than the injection spot size. These changes in the spatial maps and spin precession due to an external magnetic field as a function of the magnetic tip position can help obtain information regarding spin diffusion, precession, and relaxation with enhanced spatial resolution. The strong field gradients produced by local spin features can also increase the signal in magnetic force microscopy of the sample.


Mathematical and Physical Sciences: 1st Place (The Ohio State University Denman Undergraduate Research Forum)


Spin Diffusion, Spin, Semiconductor, Gallium Arsenide, Imaging