We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perpendicular-to-plane transport. These results show that low-field spin-dependent transport in manganates can be accomplished, the magnitude of which is suitable for magnetoresistive field sensors.
The discovery of two-dimensional electron gas (2DEG) at well-defined interfaces between insulating complex oxides provides the opportunity for a new generation of alloxide electronics. Particularly, the 2DEG at the interface between two perovskite insulators represented by the formula of ABO 3 , such as LaAlO 3 and SrTiO 3 , has attracted significant attention. In recent years, progresses have been made to decipher the puzzle of the origin of interface conduction, to design new types of oxide interfaces, and to improve the interfacial carrier mobility significantly. These achievements open the door to explore fundamental as well as applied physics of complex oxides. Here, we review our recent experimental work on metallic and insulating interfaces controlled by interfacial redox reactions in SrTiO 3 -based heterostructures. Due to the presence of oxygen-vacancies at the SrTiO 3 surface, metallic conduction can be created at room temperature in perovskite-type interfaces when the overlayer oxide ABO 3 involves Al, Ti, Zr, or Hf elements at the B-sites. Furthermore, relying on interface-stabilized oxygen vacancies, we have created a new type of 2DEG at the heterointerface between SrTiO 3 * Corresponding author. Email: yunc@dtu.dk TOPICAL REVIEW---Oxide Interfaces 2 and a spinel γ-Al 2 O 3 epitaxial film with compatible oxygen ions sublattices. The spinel/perovskite oxide 2DEG exhibits an electron mobility exceeding 100,000 cm 2 V -1 s -1 , more than one order of magnitude higher than those of hitherto investigated perovskite-type interfaces. Our findings pave the way for design of high-mobility alloxide electronic devices and open a route towards studies of mesoscopic physics with complex oxides.
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