There are many electronic and magnetic properties exhibited by complex oxides. Electronic phase separation (EPs) is one of those, the presence of which can be linked to exotic behaviours, such as colossal magnetoresistance, metal-insulator transition and high-temperature superconductivity. A variety of new and unusual electronic phases at the interfaces between complex oxides, in particular between two non-magnetic insulators LaAlo 3 and srTio 3 , have stimulated the oxide community. However, no EPs has been observed in this system despite a theoretical prediction. Here, we report an EPs state at the LaAlo 3 /srTio 3 interface, where the interface charges are separated into regions of a quasi-two-dimensional electron gas, a ferromagnetic phase, which persists above room temperature, and a (superconductor like) diamagnetic/paramagnetic phase below 60 K. The EPs is due to the selective occupancy (in the form of 2D-nanoscopic metallic droplets) of interface sub-bands of the nearly degenerate Ti orbital in the srTio 3 . The observation of this EPs demonstrates the electronic and magnetic phenomena that can emerge at the interface between complex oxides mediated by the Ti orbital.

Interfacial spin glass state and exchange bias in manganite bilayers with competing magnetic orders

The correlated charge, spin, orbital, and lattice degrees of freedom in transition metal oxides make them an attractive platform to explore rich physics and potential applications. [ 1,2 ] Oxide interfaces offer even more exciting opportunities due to the emerging effects such as broken inversion symmetry, interfacial exchange interaction, and spatial confi nement. [ 3,4 ] Heterostructures composed by non-magnetic band insulators LaAlO 3 (LAO) and SrTiO 3 (STO) have attracted much attention recently, and the unexpected conduction is often linked to the electronic reconstruction at the polar (LAO)-nonpolar (STO) heterointerface. [ 5,6 ] One defi ning feature of the interface conduction is the thickness dependence, i.e., it is insulating when the LAO thickness is below four unit cells (u.c.), whereas the conduction emerges above the critical thickness. [ 7 ] Furthermore, the carriers in the two-dimensional electron gas (2DEG) are confi ned within several nm near the interface as a result of broken symmetry, and the profi le of distribution has a sensitive dependence on the carrier density. [8][9][10][11][12][13] Based on the 2DEG at the LAO/ STO interface, nanoscale control of the insulator-to-metal transition using local probes has also been demonstrated. [ 14,15 ] The recent revelation of magnetism at the LAO/STO interface added another facet to the exciting physics. [16][17][18][19][20] Two notable sources were proposed for leading to the weak magnetism discovered in the LAO/STO heterostructures: One is the intrinsic electron reconstruction [ 16,21 ] and the other is the extrinsic oxygen vacancies. [ 22 ] In addition, the inhomogeneous distribution of magnetic dipoles as demonstrated in a recent scanning superconducting quantum interference device (SQUID) microscopy study clearly underscores the critical role of disorder in forging the magnetic landscape. [ 20 ] In spite of the efforts, [ 16,[18][19][20]23 ] the nature of magnetism discovered in samples prepared in a wide range of conditions remains as an issue of debate.To shed light on the physics of LAO/STO interface and to modulate its properties, electric fi eld effect was proven to be a powerful tool. [ 7,[24][25][26][27] In particular, an insulator-to-metal transition has been achieved by using electric fi eld gating at room temperature. [ 7 ] In these previous efforts, the STO substrates were used as the dielectric insulator in the back-gate confi guration, and high voltages of tens to hundreds of volts were required. Recently, ferroelectric Pb(Zr 0.2 Ti 0.8 )O 3 was used to bias the LAO/STO interface in a top-gate confi guration, and nonvolatile modulation of the 2DEG was demonstrated. [ 28 ] As a breakthrough in such electric fi eld effect studies, electric double-layer transistors (EDLTs) with the top-gate confi guration were employed to trigger the transformation of ground states in some key materials. [29][30][31] However, so far there has been no report on applying this powerful technique to exploring the transport properties of oxide interfaces.In...

Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt=LaAlO 3 =SrTiO 3 heterostructures, where the conducting layer near the LaAlO 3 =SrTiO 3 interface serves as the ''unconventional'' bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the LaAlO 3 =SrTiO 3 interface and the creation of defect-induced gap states within the ultrathin LaAlO 3 layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.

Although surfactants have been widely used to tailor the size, shape, and surface properties of nanocrystals and control the pore size and phases of mesoporous frameworks, the use of surfactants as reaction media to grow chalcogenide crystals is unprecedented. In addition, compared with ionic liquids, surfactants are much cheaper and can have multifunctional properties such as acidic, basic, neutral, cationic, anionic, or even block. These features suggest that surfactants could be promising reaction platforms for the development of novel chalcogenide crystals. In this work, we used chalcogenidoarsenates as a model system to demonstrate our strategy. By using three different surfactants as reaction media, we obtained a series of novel thioarsenates ranging from a zero-dimensional (0D) cluster to a three-dimensional (3D) framework, namely, [NH(4)](8)[Mn(2)As(4)S(16)] (1), [Mn(NH(3))(6)][Mn(2)As(2)S(8)(N(2)H(4))(2)] (2), [enH][Cu(3)As(2)S(5)] (3), and [NH(4)][MnAs(3)S(6)] (4). The band gaps (estimated from the steep absorption edges) were found to be 2.31 eV for 1 (0D), 2.46 eV for 2 (1D), 1.91 eV for 3 (2D), and 2.08 eV for 4 (3D). The magnetic study of 4 indicated weak antiferromagnetic behavior. Our strategy of growing crystalline materials in surfactants could offer exciting opportunities for preparing novel crystalline materials with diverse structures and interesting properties.