Structural and Magnetic Properties of LaCoO₃/SrTiO₃ Multilayers

Structural and magnetic properties of the LaCoO₃/SrTiO₃ (LCO/STO) multilayers (MLs) with a fixed STO layer of 4 nm but varied LCO layer thicknesses have been systematically studied. The MLs grown on Sr_0.7La_0.3Al_0.65Ta_0.35O₃ (LSAT) and SrTiO₃ (STO) exhibit the in-plane lattice constant of the substrates, but those on LaAlO₃ (LAO) show the in-plane lattice constant between those of the first two kinds of MLs. Compared with the LCO single layer (SL), the magnetic order of the MLs is significantly enhanced, as demonstrated by a very slow decrease, which is fast for the SL, of the Curie temperature and the saturation magnetization as the LCO layer thickness decreases. For example, clear ferromagnetic order is observed in the ML with the LCO layer of ∼1.5 nm, whereas it vanishes below ∼6 nm for the LCO SL. This result is consistent with the observation that the dark stripes, which are believed to be closely related to the magnetic order, remain clear in the MLs while they are vague in the corresponding LCO SL. The present work suggests a novel route to tune the magnetism of perovskite oxide films

Highly Mobile Two-Dimensional Electron Gases with a Strong Gating Effect at the Amorphous LaAlO₃/KTaO₃ Interface

Two-dimensional electron gas (2DEG) at the perovskite oxide interface exhibits a lot of exotic properties, presenting a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO₃-based 2DEG, here we report on the fabrication of high-quality 2DEGs by growing an amorphous LaAlO₃ layer on a (001)-orientated KTaO₃ substrate, which is a 5d metal oxide with a polar surface, at a high temperature that is usually adopted for crystalline LaAlO₃. Metallic 2DEGs with a Hall mobility as high as ∼2150 cm²/(V s) and a sheet carrier density as low as 2 × 10¹² cm^–2 are obtained. For the first time, the gating effect on the transport process is studied, and its influence on spin relaxation and inelastic and elastic scattering is determined. Remarkably, the spin relaxation time can be strongly tuned by a back gate. It is reduced by a factor of ∼69 while the gate voltage is swept from −25 to +100 V. The mechanism that dominates the spin relaxation is elucidated