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It was found that by using the same α-Fe2O3 target in fabrication process, an oxygen-deficient and an oxygen-sufficient atmosphere facilitated the formation of Fe3O4 and α-Fe2O3, respectively. The Au/α-Fe2O3/Pt heterostructure showed a memristive bipolar resistance switching. A clear difference was observed in the transport and magnetic properties between the two resistance states. The enhanced conductivity and magnetization in the Au/α-Fe2O3/Pt heterostructure are believed to result from an enhanced electron hopping between Fe3+-Fe2+ pairs and Fe3+-O-Fe2+ double exchange coupling effect. The enhanced Fe2+ comes from a redox transition between two phases (one behaves like Fe3O4 and the other like α-Fe2O3), due to the electrochemical migration of oxygen vacancies. [ABSTRACT FROM AUTHOR]

By controlling the temperature and oxygen partial pressure, well polycrystalline Fe3O4 thin film on Pt substrate was fabricated, using a stoichiometric α-Fe2O3 target. A ferrimagnetic hysteresis loop and a Verwey transition at about 130 K were shown in the results of magnetic measurement. A sharp hysteretic resistance switching below Verwey transition temperature (Tv) was observed in I-V tests of the Au/Fe3O4/Pt heterostructure. Enlarged hysteresis by larger pulse delay and suppressed metal-insulator transition by larger source currents indicated that enhanced local Joule heating effect played an important role in the hysteresis of resistance switching. [ABSTRACT FROM AUTHOR]

We present a study of the anisotropic properties of two-dimensional electron gases formed in GaAs/AlGaAs heterostructures in which InAs self-assembled quantum dots have been inserted into the center of a GaAs quantum well. We observe an anisotropic mobility for the orthogonal [1¯10] and [110] directions. The mobility in the [1¯10] direction was found to be up to approximately twice that in the [110] direction. It is suggested that the interface roughness scattering due to the inserted InAs material could be a cause for the large anisotropies in mobility. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pronounced bipolar resistance switching with a good retention property has been observed in CeO2/PrBa2Cu3O7-δ/Pt heterostructure. The low resistance state and high resistance state exhibited distinguished ferromagnetic signals, as compared to the nearly non-magnetic initial state. It is found that the migration of the oxygen vacancies under electric field is mainly responsible for the electric and the magnetic changes. The modified interfacial electronic structure by the oxygen vacancy migration and the trapping/detrapping of the carriers leads to the resistance switching. The exchange interaction of the hydrogen-like orbitals formed around the singly occupied oxygen vacancies in CeO2 is accounting for the emerged and modulated ferromagnetic signals. Temperature dependence of resistance in the low resistance state follows a variable range hopping law, further confirming that the amount of oxygen vacancies in the CeO2 layer directly affects the hydrogen-like orbital radius, which determines the strength of the ferromagnetic coupling. [ABSTRACT FROM AUTHOR]

We reported the resistance switching (RS) behavior in the epitaxially grown CeO2/ La0.7(Sr0.1Ca0.9)0.3MnO3 (CeO2/LSCMO) heterojunctions on SrTiO3 substrate. The CeO2/LSCMO device displayed improved switching characteristics as compared to that of metal/manganite device. The switching threshold voltage showed a strong dependence on the thickness of the CeO2 layer, where a minimum/maximum thickness was required for the appearance of the resistance switching. Both set and reset threshold voltages increase with the increase of the CeO2 layer thickness due to the trap-assisted electron tunneling effect. In the meantime, the defects or vacancies in the CeO2 films, in particular, the concentration of the defects or vacancies in the interface between CeO2 and LSCMO, have a significant impact on the switching effect. These results suggest that the electron tunneling accompanied by a trapping/detrapping process at the interface is likely responsible for the RS effect in the insulator/manganite system. [ABSTRACT FROM AUTHOR]