Neutron Scattering Studies of Magnetic Semiconductors and their Superlattices

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9510241 Furdyna The objective of the proposed research is to investigate magnetic ordering and magnetic interactions in cubic manganese telluride and manganese selenide, as well as in their multilayers and alloys, by means of neutron scattering techniques. These materials, which do not occur naturally but can be fabricated in this crystal phase by molecular beam epitaxy (MBE), hold great fundamental interest because their manganese sublattices consititute frustrated Heisenberg antiferromagnets governed by short-range interactions. MBE provides the opportunity to vary in a controlled fashion various degrees of freedom which directly affect their magnetic behavior, such as strain, magnetic layer separation, dilution, and dimensionality, thus accessing a variety of fundamentally new problems in magnetism. The research will focus strongly on investigating the coupling between magnetic layers in order to understand the nature and range of manganese-manganese interactions beyond those involving nearest neighbors. New neutron scattering experiments will be initiated, using ultrathin layers of these materials, in an effort to observe the crossover from three to two dimensions, and ultimately to investigate magnetic interactions in the two-dimensional limit itself. Samples will be prepared at Notre Dame University, and the neutron scattering experiments will be conducted primarily at the Missouri University Research Reactor. %%% The objective of the proposed research is to investigate magnetic ordering and magnetic interactions in thin layers of cubic manganese telluride and manganese selenide, as well as in multilayers and alloys thereof, using neutron scattering techniques. These materials, which do not occur naturally but can be grown in this structural form by molecular beam epitaxy (MBE) hold great fundamental interest because the manganese ions form "frustrate d" antiferromagnetic structures governed by short-range interactions between the ions. The growth technique permits the controlled variation of factors that directly affect the magnetic behavior, such as strain, separation of the magnetic layers, dilution of the magnetic ions, etc., thereby providing access to a range of fundamentally new problems in magnetism. The research will focus strongly on investigating the coupling between magnetic layers in order to understand the nature and range of interactions between the manganese ions. New neutron scattering experiments will be initiated, using ultrathin layers of these materials, in an effort to observe the crossover from three to two dimensional magnetic behavior. Samples will be prepared at Notre Dame University, and the neutron scattering experiments will be conducted primarily at the Missouri University Research Reactor. ***