Advancements in semiconductor circuitry have revolutionized data processing in recent decades. Simultaneously, developments in magnetic-based media have expanded capabilities for permanent data storage. An emerging technology called spintronics integrates magnetic components with semiconductor devices and has the potential to increase processing power by many orders of magnitude. In the ongoing search for materials combining properties of ferromagnets and semiconductors, researchers have discovered a promising new class of dilute ferromagnetic semiconductors that includes Ga_xMn_(1-x)As.NIST researchers at the NIST Center for Neutron Research (NCNR) have begun to probe these structures with polarized neutron reflectometry and small-angle neutron scattering to determine the nature and relevant length scales of cooperative magnetic behavior in these materials. Polarized neutron reflectometry is ideally sited to the study of these structures because it provides depth-dependent magnetic profilometry of buried magnetic layers with sub-nanometer resolution. Since the equilibrium Mn solubility in GaAs is low (less than seven percent), the ferromagnetic transition temperature of the homogeneous alloy is limited to 110K, far below feasible temperatures for device operations.
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