Interlayer magnetic coupling in ferromagnetic semiconductors for spintronic applications. (News Briefs).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 Refers to a material, such as iron and nickel, that can be easily magnetized. See MRAM. semiconductors that includes [Ga.sub.x] [Mn.sub.1-x]As. NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. researchers at the NIST Center for Neutron Research (NCNR) have begun to probe these structures with polarized A one-way direction of a signal or the molecules within a material pointing in one direction. neutron reflectometry and small-angle neutron scattering Small angle neutron scattering (SANS) is a laboratory technique, similar to the often complementary techniques of small angle X-ray scattering (SAXS) and light scattering. These are particularly useful because of the dramatic increase in forward scattering that occurs at phase to determine the nature and relevant length scales of cooperative magnetic behavior in these materials. Polarized neutron reflectometry is ideally suited 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 110 K, far below feasible temperatures for device operations. To stabilize a higher concentration of Mn, researchers at University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). Santa Barbara fabricated digital GaAs/Mn superlattices by molecular beam epitaxy A technique that "grows" atomic-sized layers on a chip rather than creating layers by diffusion. techniques. NCNR and University of Utah The University of Utah (also The U or the U of U or the UU), located in Salt Lake City, is the flagship public research university in the state of Utah, and one of 10 institutions that make up the Utah System of Higher Education. researchers have probed digital structures with polarized neutron reflectometry to determine how the interaction between the Mn layers changes as a function of their separation distance. The experiments show that Mn layers spontaneously align parallel to each other after cooling in zero magnetic field. These early polarized neutron reflectometry measurements provide guidance for fine-tuning the structure to maximize the ferromagnetic ordering temperature as well as to establish other fundamental spintronic properties of these innovative semiconducting materials. Contact: Julie Borchers, (301) 975-6597; julie.borchers@nist.gov or Kevin O'Donovan, (301) 975-8380; kevin.odonovan@nist.gov. |
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